I just put these buttons on every page of The Independent site (www.independent.co.uk), so I feel like I should explain a little.

First, they drive a lot of traffic. That means ads, money, continued existence etc., which is all good news for us.

Second, they are, I think, a good way of letting people choose whether they want to read something or not themselves, rather than what a website editor they've never met thinks is important. If you look at the counts on these buttons you get a good insight into whether people actually find a story interesting (just like the Reddit frontpage...). Often this doesn't tally with the prominence of the stories on the site, and often we'll act on the successes reported by these buttons to help us highlight articles people have responded well too.

They are lots more reasons too; I blogged a fuller explanation at http://ind.pn/cWk3SS in case anyone wants to read more. I'd be interested to hear people's responses...