wannaBe, you don't seem to have any other point to make, and I'm bored of seeing "you shouldn't post on the internet if you're worried about people seeing it", but I'll reiterate my answer to your point again:
None of us are stupid enough to think that we're completely anonymous here. However, many of us go to fairly great lengths to ensure that we are as anonymous as it is possible to be. I have posted things here before which could not be proven to be written by me, although there may have been a question of it.
This 'like' button encourages people to plaster MN threads all over their facebooks in a way that the far more subtle FB link in the top bar did not do previously. Yes, one could click that before. Or yes, one could easily c+p a link from here to FB (or anywhere else). But having a friendly, innocuous-looking 'like' button on each post, much like there is on many other websites, is just asking people to click it.
I wish MNHQ would stop being so disingenuous and admit that this is a money-making exercise and that they're going to continue with this, despite the very real concerns of some of their most prolific posters.