Comment by pavel_lishin

I'm not suggesting that this is trivial to implement, but in principle, wouldn't it be fairly simple for Pinterest to identify these guys based on their 'social networks'? If a group of accounts only 'pins' posts of other accounts in that same group, that suggests either a spambot farm, or a very inclusive group of friends. False-positive detection could be decreased by looking at account sign-up dates, or profile photos.