This was happening with beta versions and is happing now that I upgraded to 7.x-3.0.
I disabled the 'Commons Like' module (as I won't use it) but the 'like' link (should it be a button?) is still there on group and content pages, except for the wikis (and that makes it even more confusing).
I can't understand why is there a module "working" when it's disabled. It even says 'You voted '1'.' when I click on it.