µBlock enables Fanboy's social blocking list by default. If you want your Twitter/FB buttons and so forth back, you can turn it off in the subscription options.
The problem is that it doesn't just block the buttons, it blocks assets that just happen to have those names that are unrelated to the buttons as well.
Both the Chrome and Opera versions did for me, and quite recently too: only switched on Chrome about a month ago at most, and I've only even had Opera installed for about a week.
