Being pinned is a thrill for some.
People that sell things tend to find Pinterest useful. Maybe that's why Rakuten, the behemoth Japanese e-commerce company, invested millions in Pinterest. Maybe that's why Pinterest is conviently hosted on Amazon'z servers.
Etsy Shopkeepers appear to appreciate having their images pinned. In fact, they rave about the flattery and the exposure, responding to being pinned much in the way that pinners expect. Minor objections seem to center around pinners wanting to make the projects themselves rather than purchasing the items. There are, unfortunately, very few quantitative evaluations of actual Pinterest traffic and conversions from the Etsy shopkeepers.
The Print-On-Demand (POD) site 1x.com, after toying with the "pin it" button, has removed it. In the words of founder Ralf Stelander, "We have decided to remove the pinterest button, it generated very little traffic anyway."
One might guess Pinterest may not doing much for the POD business model.