It's like you wrote that straight out of my brain. After having LinkedIn deemed necessary by Yet Another Recruiter the other day, I signed up last week... and it felt terrible. I've resisted the reeking phoniness of Facebook et al, despite being ironically ridiculed by damned near everyone I know, since the start of this appalling revolution in social networking, and now I'm conscientiously signing up to a site that uses the term "Action Items" in its navigation menu? Naturally, since I signed up, a cavalcade of people with names I vaguely remember from my working past suddenly want to be my "friend" without being my friend. I grit my teeth and acquiesce, because more connections make me look good.
So, I did it, but it's about as sincere as spooning with a hooker. I'm dead-certain that myself and the parent poster aren't the only two who have signed up for the same reasons, and I can easily imagine that the eventual backlash against LinkedIn will arise from an increasing number of users who are there due to professional compulsion and have zero interest in any of its God-damned "Action Items."