As a general rule, I try not to take on any activities that give me an excuse to procrastinate on my thesis; so when I do end up procrastinating (which is a lot), I only allow myself to do frivolous stuff, like post to SlashDot. So now, however many years in, I have spent hundreds of hours writing throw-away comments in a community so large and transient that establishing a real reputation is impossible. It has occured to me lately, that I could have instead spent this time contributing to open source projects or at least posting to a site with real community — if I had been doing so, perhaps I would be able to network myself with a job or at least real-life friends in my future.
Instead, for the last two weeks or so I've been longingly gazing at LinkedIn. The buzz is such that I figure I won't get my next job by online social networking, but it'll probably contribute to my next, next job. (I suppose at this point I should admit that Cory Doctorow was on to more with Eastern Standard Tribe than I was first willing to admit.)