one thing I should probably add to what I said: I don't actually mind at all the idea of people I used to know being able to find and contact me again online. I don't like the idea of what I get up to day to day just being out there for anyone to peruse though. I'd like to know that I've got some idea (most of the time) of who is (potentially) reading personal stuff I actually talk about.

And of course there's the whole bit about not wanting to volunteer too much information for some commercial operation to make use of in some way that suits them.