Pinterest is by FAR the easiest social network to spam right now. Quite possibly the easiest ever to spam. It requires almost no work to get started and no money to invest. You just have to know how the system works and how you can fix it to your advantage.
There's always someone. Worth a read though, as it helps to illuminate (a bit) some of the growth of pinterest. It's not all suburban mom's pinning pictures of the rooms they want to make for their kids.