I think stalking people on social networks is also a net negative experience. I realized I should spend less time worrying about what other people are doing with their lives and focus more on my own.
There was also a recent NY Times article about how employers use LinkedIn candidates contacts to disqualify them for employment[1]. So LinkedIn can actually be detrimental to your career.
I just don't think LinkedIn adds anything. Businesses and recruiters use it to get your email to target you for spam. But what do you get out of it and think, if there wasn't a LinkedIn would you be out of a job right now?
[1] http://www.nytimes.com/2014/11/09/technology/on-linkedin-a-r...