I wouldn't mind knowing who liked a post I made if they wish to be known. If I'm liking someone's post I don't see why I should keep myself anonymous to them either. As long as users had the option to block their name from being seen by who they liked if they wish, I don't really see why the change should be a problem then.
One question would be is it retroactive or on a like by like basis? Will past likes automatically show your name or will your name remain hidden if you decide to select that option? If you choose to hide your name for now, but change the setting later so it shows up, will your old likes remain nameless?