Being able to search and find people by the names they actually use on a day to day basis is actually a feature I value very highly in a social network. Being able to hide from abusive people in one's past is actually a feature I value very highly in a social network. I know a number of people -- transpeople, people from other countries, people who just don't like their given name -- who don't use their "real" name in "real" life. Why should facebook require one's legal name when no in person congregation requires you to wear a name badge that identifies you with a name you may not be comfortable with?

If you don't like Facebook's value proposition, you're always free to build your own social network with the features you like. Nobody forces you to use Facebook.

Because it's your legal name?

You may not be aware that in some jurisdictions (Quebec is an example), marriage is not a sufficient legal reason to change your legal name, yet most people informally identify with a spousal name change. It would seem like an overstep for Facebook to regulate against this by policy. That's only one of many, many examples where people shouldn't be forced into using their legal name simply BECAUSE it's their legal name.

The UK, for one, does not have the concept of a 'legal name'. Your name is whatever you choose to call yourself.

Even a deed poll has no official weight, it's just a statement of a name you have chosen. Hence 'poll' instead of 'certificate'.

What is so important about displaying the legal name, especially in cases (like the GP explained) where nearly no-one in ones social environment knows it? If Facebook had legal reasons to know it they still could make displaying it optional.

No, you value an environment safe enough that people can use their common name -- the one that you would likely know them by.

You do not care about government recognized names. And declaring a network safe for personally identifying information does not necessarily make it so.

In fact, it's an absolute bare minimum for an even remotely usable social network.

Because IRC, ICQ, MSN, Lunarstorm, Instagram, all those PhpBB and vBulletin boards we all used to use (and still do) was never even "remotely usable"....

The only way facebook differs to most of them is that it markets itself to being a general social network, not one specifically about programming, horses, biking, photography or another specialized field. Finding your friends by alias was never a problem, it's just like asking someone for their phone number.

Why? There are tons of online communities that mostly know each other by handles and still might profit from using facebook. Right now they stay entirely seperated unless everybody is OK with linking their "real" identity to their online one.

(If I wanted to contact you the ability to search for a real name would be completely useless to me. Being able to find someone called "baddox" might help. If that name then is linked to your real identity or not would be a different matter)

This can be an optional disclosure made by people who wish to be found by their real name.