Typically I've written the article before passing it on to someone, so in those cases, obviously the question doesn't apply. In the latter case, if someone asks for me to e.g. write about tax credits for their site, then it's only polite for them to allow us to include a byline without nofollow.
> And what links are you requiring in the byline?
Hah, whatever I can get :-) Depends on the site, obviously, but if I can get links to some of our topic pages with the right text, I'll go for that! (e.g. http://www.ec1capital.com/blog/rd-tax-credits-explained).
We don't "ask to guest post" as a company, though I've offered to write some good original content on occasion, but only in person and with no pressure.
Observations: 1. As a product search experience, that is still horribly broken.
2. It is still good for the web, incentivizing you to create quality content.
Occasionally I have written a full blown article and suddenly realised it would be better suited for another site (eg techcrunch) and approached the editor there to ask if they would like to publish that specific article, but I don't do blanket "can I write something for you". That would be highly hypocritical!
GrantTree is ranked pretty high against our competitors on several keywords that are important to us. This was all entirely through whitehat SEO within about a year of setting out to do it. We've just written lots of high-quality content on our blog, and then contributed genuine, original articles to other sides and got them to include a link to GrantTree or to one of our topic sub-pages (like http://granttree.co.uk/tax_credits ) in the byline. We've never bought links, nor will we ever buy links.
Now, GrantTree's context is not super-competitive like, say, Expedia or RapGenius... but we do have competitors. So competing with good, well-structured content and genuine contributions to other sites does work - at least in some contexts.
Also, I'm frequently on the receiving end of these "your blog/site/whatever is awesome and we'd love to publish a high-quality article on your blog and we'll even pay you for it" emails, and as far as I'm concerned they are spam. I never even bother replying to them.
I'll be happy if Google nails those spammy bastards to the wall - both the paymasters and the so-called bloggers.
(Note: this makes no judgement on the claim that Expedia is partaking in this)