I've seen all the anti-Facebook sites which detail how they're collecting details etc, and who runs it and who knows who... but at the end of it all our details are pretty much out there whatever we do now (paid by Credit Card anywhere... kerching, some info being distributed) so what the hell!!
I do find it rather useful to keep messages of a social nature all together on the site, not intermingled with my work stuff (where they inevitably disappear amongst all the junk from people there!) and it's a laugh to see people's status updates - gives you a brief and daily (assuming you visit it each day) view of how they are without having to contact them. An almost constant reminder that they are still out there in their world, plodding along....