"Like"

I just got the achievement "Like" for posting a game on facebook.

I didn't do it. I don't even have a Facebook account.

Would anyone know the cause of this?

Very strange! I think the achievements have just been buggy. Could you have accidentally clicked on something? Maybe you clicked on a "share game on facebook" link and it says you did even though it wasn't attached to an account.

I haven't seen that button. Mind telling me where I would find such button?

and I would doubt that, I don't remember ever seeing a facebook tab on my browser.

Happened to me as well. Same with Twitter. If you click the 2 options (Facebook and Twitter) above the comment box, you'll get the achievement. Strange indeed

You get it for clicking that button from the post game modal. Doesn't really matter if it actually works. so could have been a misclick.