Pinterest should sell internal data on which items get pinned the most from which retailer in which time period.
IE: This necklace got pinned the most from Macys.com during the week before Valentine's Day. I'm sure JCPenny, BlueNile etc would find that data useful.
I'm already seeing Pinterest tags on clothes at Nordstrom's. Your idea would definitely help move that along. They have a unique opportunity here to help a lot of retailers. I'd like to see the company do more than just advertising.
IE: This necklace got pinned the most from Macys.com during the week before Valentine's Day. I'm sure JCPenny, BlueNile etc would find that data useful.