LinkedIn's business model is that regular people join for free and recruiters pay for an account that lets them contact those people. Some skeevy recruiters us

LinkedIn's business model is that regular people join for free and recruiters pay for an account that lets them contact those people. Some skeevy recruiters use the "I already know this person" button when they don't, to avoid paying LinkedIn. Because they're breaking the rules of the site, I think it's correct to call them spammers. The recruiters who contact without lying to do so aren't spammers, since that's indeed a large part of what the site is for, and you agree to such contact when you join. (And I believe you can turn off such contacts in the preferences, though I can't double-check since I just closed my account.)