I'm going to go against the grain here and say I don't think it's necessary. Perhaps because I'm not on FB and never have been on FB I fail to see the appeal. IMO if I 'like' someone's post I would be more inclined to say so (to express my appreciation) rather than just take the lazy option of clicking a button. Either way, it wouldn't really bother me because it would just be a feature I'd overlook.