According to Alexis Kleinman of the Huffington Post, there are a whole lot of non-humans active on Facebook:

Facebook loves to talk about its ridiculously high number of users. Yes, Facebook has a whole lot of accounts, but many of them aren’t humans. eMarketer released an analysis of Facebook’s audience, and it turns out more than 10 percent of Facebook’s reported monthly users are not human. Over 100 million active Facebook users are pets, objects or brands.