I regularly use StumbleUpon to discover new websites I will probably like and del.icio.us to bookmark and share them but I don’t really use their user community features.
I have a LinkedIn account to stay in touch with past colleagues career paths and also a Google Reader account to keep track of blogs I read.
But this isn’t sufficient, I need a lot more software services, like keeping track of all the persons I’ve known. I mean, even the sites they viewed, the books they read and the movies they liked, only if they allow it, of course, I’m not Big Brother. 😉