and more generally any one deemed of inferior status and/or easy to prey on (women commonly being slotted in these categories either way), the number of people who will seem perfectly nice around their colleagues but will abuse staff (e.g. serving or cleaning agents, or secretaries) at the drop of a hat is astounding and disheartening.
It's not just that someone might have to deal with an overwhelming amount of unwanted interest from a single person, but that the aggregated polite inquiries from dozens or hundreds of interested coworkers and colleagues could add up to something overwhelming. It's like littering.
So while being in a relationship with a co-worker may be fine, starting a relationship with a co-worker is tricky. It's like why you shouldn't hit on wait staff or flight attendants: they are there because it is there job. Your co-workers come into work every day for the same reason.
Yet this behavior is romanticised is popular culture, and has been from the dawn of time up to and including the present: Oddyseus and Helen of Troy, Shakespeare's "The taming of the shrew", tons of Fred Astaire movies, as well as modern movies like "Ghost", "Life is beautiful", "Chasing Amy", TV shows like "Sex and the city"... I could go on. Lucikly I don't need to, since TVtropes has a site dedicated to this character (the "dogged nice guy"). And note that many of these are targeted at, and very popular with, women (who are usually at the receiving end of the initially-unwarranted attention). Apparently this behaviour can walk a thin line between illegal and very very romantic.
(Oblig. http://xkcd.com/609 )
(Also "The Taming of the Shrew" is firmly in the "oh fuck no" category of 21st century society)
Beyond that, the bigger issue to my eye is that it doesn't always work out. If your boss flirts with you and you aren't interested, that puts you in an awkward position. What if saying no makes them upset with you, or just negatively colors their perception of your work in the future? (Human beings being what we are, it's hard for a negative feeling about someone in one context to be entirely compartmentalized away from our judgement about them in another.)
Also, whether it works out or not: If romantic attachments between supervisors and subordinates are an accepted part of the culture of this workplace, what are the odds that the boss's attraction to you factored into your hire? Are your colleagues aware that the boss is attracted to you? Does that undermine their confidence that you got your position based on talent? Does it undermine your confidence that you got the position for the right reasons? (Might the boss think that you owe them some sort of sexual payoff for the job? There's a comforting thought as you try to do your job.)
I'm not saying that any of those suspicions or worries are justified in most cases! I'm sure that most people do a decent job of separating their work responsibilities and their personal lives, even in these sorts of circumstances. But a culture that accepts supervisor-employee relationships invites this class of concerns in a way that a culture that prohibits them would not. (And maybe my thoughts here really are influenced by thinking about this in a grad student context: Ph.D. advisors have a truly astounding amount of power over their students' futures.)
People are being trained to make these leaps even if there are no facts to back them up. You might _feel_ your boss is treating you differently because she asked you out, but should we all adjust behavior to accommodate _potential_ negative impressions in a lowest-common-denominator kind of way (You seem to agree that we should not...)? These discussions tend to assume the absolute worst outcome regardless of incidence.
Some quick googling suggests 30% of office romances lead to marriage. Even if that stat is wildly inaccurate, it still feels bizarre to tell so many people they should have taken one for the team (not had a relationship).
My reason for preferring an outright ban on supervisor/employee relationships is that they can have nasty effects on the entire workplace culture, that they can be exploitative or feel exploitative, and that based on many reports neither of these effects is particularly rare. Good leadership can't only be fair, it has to also cultivate a belief among employees that it is fair.
Is there a cost to this in lost opportunities for positive relationships? Absolutely. But even the highest-level executive won't have more than a few thousand people declared "off limits" to them by this: surely that's a drop in the bucket compared to the total population of the cities or communities where they live.
When you read about these, the authors almost exclusively present it as the person in the dominant position somehow taking advantage of the other. Are you equal, though, in your condemnation of e.g. the flirty student successfully seducing her professor? This happens. Is your message to her that she has no idea what she is doing, and that she's setting back gender equality by doing so? The answer is usually dodged because admitting the situation happens (both participants being into it) pollutes the desired narrative- That one partner has no agency by dint of the power imbalance.
re: your 2nd paragraph, can you provide some links? You present it as common knowledge. What's the actual incidence of negative outcomes? If it's, say, 15%, that means 85% have positive outcomes, and you want to tell those people to go pound sand. I find that unreasonable.
As I've learned more about feminism in recent years, I've found myself thinking about Clinton and Lewinsky again, and I'm much more on her side now. (I still don't entirely buy the age-based concern that she raised.) Even if the relationship was entirely consensual and entirely initiated by Lewinsky and they were both happy about it, that still doesn't mean that it was healthy for the morale of their workplace, for all the reasons I listed before (quite apart from Kenneth Starr). I don't put primary blame on Lewinsky for that (though as an adult she ought to have known better): as the "boss" in the situation, it was Clinton's responsibility to turn her down, at least until he was out of office or she no longer worked for the federal government.
As for the flirty student seducing the professor, it takes two to tango. Speaking as a professor who's been pretty clearly flirted with at least once, I can tell you that I had no trouble at all indicating my lack of interest. I'm not condemning her for "setting back gender equality", but it was blindingly clear to me as the person on top of the power imbalance that anything other than a professional relationship would absolutely call my objectivity in the class into question. (In that particular case it didn't help that our broader conversation that day was about her concerns about her grade, but I would have had the same issues even if she'd had a solid A.) If a pairing like that were truly meant to be, the student would be welcome to come back and make a proposition after commencement. In the meantime, I can assure you that having my undergrads be "off limits" romantically doesn't feel like an undue burden on my love life. (Admittedly, I've been married the whole time I've been a professor. But the point still stands.)
Re: your last paragraph, about my 2nd paragraph: The original article that this whole thread is responding to is literally a collection of quotes and stories from women who found this sort of environment miserable and want it to change. If that's not enough for you, I don't think me Googling to find you more examples is likely to change your mind.
Clinton morally erred by breaking his vows to his wife, but if we set that aside, he did not do anything wrong by the simple act of having sex with Lewinsky. Let's assume, though, that the power differential argument _is_ valid- Who _could_ he engage in a relationship with, being President? Not politically powerful women, because his power is always going to be greater. Maybe other world leaders only? Only world leaders in the G8? He has no peers.
The student/professor example has a few _practical_ concerns regarding why you might want to avoid that situation and you've laid those out, and I agree. But ethically there would be no cause for objection unless actual grade massaging was occurring. That's not a given. In other words, appearance of impropriety is a practical objection, not an ethical objection. I'll zing any professor for taking advantage, express or implied, of one of her students but I will not automatically assume something shady is happening without evidence.
Anecdotes are not data. If we can show that the majority of these relationships are negative, that's a stronger case, but still not worth blanket-ruling the exceptions out of existence.