The solution does not work everytime. We write around 10 to 20 posts a day on our website that we don't want on facebook/twitter, and I would say that at least 2 or 3 (no idea why) goes to facebook/twitter either way (the checkbox somehow gets checked).
So I'm guessing like someone said above, the solution interferes with other functions. This should really be built-in the plugin by the developers. Any news?