Combination of "click fraud" and data mining
Facebook needs to get a handle on this. Its main selling point to advertisers is the quality of their data and how well targeted its demographics are. This kind of contamination renders Facebook useless for that purpose, which is its real purpose of its existence.
Last night I just got a invite to see pictures from one of my pastors on a dating site, which was the result of a rouge Facebook app harvesting her address book. This kind of nonsense is wearing people out.