This is important since these ads are highly targeted based on your personal information from your profile.

Before, Facebook allowed you to give an ad a thumbs up or a thumbs down. That was simple enough, but it wasnt exactly consistent with the approach used on regular Facebook content like status updates, which of course include the like feature. Facebook evidently decided they might as well make the whole thing uniform, because now instead of the thumbs upthumbs down, the options are now like and x. They work the same way, but they just fit better with the rest of the site now.