The big problem here isn't detecting bots. Sure, in this one company's case bots may be the problem; but in general, it's detecting behavior that you are paying for that doesn't make you any money. There may be real users who click "like" a lot; they may do it because they're paid, or they may do it because they're bored and trying to see how many "likes" they can collect. It doesn't really matter; none of them are very valuable to an advertiser.

Rather than trying to explicitly filter bot traffic, they should try to quantify the value of particular "likes". For instance, a user who demonstrably clicked through and purchased something is much more valuable than one who "likes" 10,000 companies and has no friends, whether or not they're a bot.

And heck; a bot that has thousands of followers who all buy lots of things is valuable too. Maybe someone created a particularly effective meme-generator bot, and people who follow that bot are likely to buy ironic T-shirts. Whether or not a user is a bot isn't all that relevant; it's whether that user's activity correlates with you making sales.