A like is the legal currency of Facebook, and an accepted currency in most areas of the internet. Likes are an extremely valuable commodity, so it is not uncommon to see people going to great lengths to get these likes. Many people go as far as posting pictures of themselves with Duck Face or posting statuses that say Lik dis if u cry evertim.
Likes cost nothing to make and you can give out infinite likes to other people. Many would claim that this makes a "like" totally worthless. But the rest of the population remains totally oblivious to this fact and works desperately to achieve these likes.