You may find it does the opposite of what you intend if your visitors don't use social media - they'll feel left out of the party and nobody likes that! There are many many reasons why someone would choose not to be on social media, and forcing them to have an account just to read an article is never going to work - they'll just leave and find the content elsewhere on the web.
Check analytics to see how socially engaged your visitors are. If they are, then I'd test it as a tactic - it may not work for long though, because it's the sort of thing Google doesn't like ('Don't do as I do, do as I say!!!!')
I bet Mr Cutts is thinking of a way to thwart your plan as I type this
Good luck whatever you do, and please let us know what the outcome is!
Amelia