I watched a youtube video of one gentleman creating 1800 accounts and spamming his small army of blogs and automating comments to encourage more interaction. The video seemed real but was quickly removed so I can't say for sure but I was left with the impression that Pinterest is ripe with abusers and there's no way to tell the difference.
With success comes fraud and I think Pinterest needs to stay ahead of the curve, I'm not sure they are right now.
There seem to be many pins that have been created by spammers on there. Spammers find the most pinned photos and repin with their own urls, probably to drop cookies or drive traffic to their own sites. When you click on some of these pictures you either get a 404 or a message saying that the page has been removed due to spam (I have reported a few too). Quite a turnoff and wondering if the inundation of the same photos together with lots of spam has anything to do with it.
Probably deleting spammers. My heavens, there's a lot of that on Pinterest. Just do a search and all the results are dominated by spam. Hopefully they do fix it, because it really has killed the search functionality at the moment.