A few years ago I cancelled my LinkedIn account for good. I'd never been a particularly heavy user, but their increasing abuse of my trust and my contact details pushed me to delete my account for good. I know that a large number of people continue to use LinkedIn, so if you're looking for my profile this will hopefully explain why I don't have one.
Other people have written about LinkedIn's practice of deceptively importing your contacts and sending them e-mails inviting them to sign up on your behalf. I even recieved these e-mails when I had a LinkedIn account; not a great way to improve the loyalty of your members.
As with any platform that lets you publish your contact details and job history, you recieve your fair share of irrelevant job offers. Unless I'm looking for a job I'm not particularly interested in speculative offers, so this was another negative.
LinkedIn has a similar model to Facebook - they allow you to construct a social graph and provide services on top of it. The difference with Facebook is that they offer me enough relevant services that I tolerate the downsides.
Why make my job history public?
LinkedIn has two main uses - it's a way to make professional contacts, and it's an online CV. The former is increasingly being supplemented by Twitter, and the latter is something I'd prefer not to be public in the first place.
So that's why
Deleting my LinkedIn account made my life a little less complicated, which is always nice. In this day and age it's becoming more commonplace to publish your personal and professional life online, but for some things I'd prefer they stay offline unless strictly necessary. The web is a wonderful tool - it's just not the tool for everything.