My presence on LinkedIn got me my last two jobs, and LinkedIn wasn't a thing when I started my first. This last job was through one of these cold-emails through a recruiter. As it has been said by other commenters, it's really what you make of it. I treat LinkedIn as a professional version of Facebook that I actually take care to prune, which really just makes it a glorified Rolodex.<p>It's also worth noting that you don't even have to be notified of all these bothersome emails, let alone reply to them, and can clearly indicate whether or not you wish to be contacted about work (granted, that can be ignored, but the good ones won't).