Saw this page on AdKeeper, the company that is trying to make online advertising bookmarkable. This could be an interesting way for Pinterest itself to make money: becoming a network for ads that people will want to hold on to. Won't be a huge stretch for them, most of the pins are already very ad like. You will easily find pins for a book, iPhone app, music, movie posters and trailers, and even payday loans.
And I already see people pinning coupons. Here's one from Jiffy Lube someone has pinned after filing out a satisfaction survey.