Pinterest has inspired me to incorporate surfboards into my practice! Haha, no. Pinterest is the fastest-growing social media site ever. Which you know because you're on it! Everyone is on it. But not everyone knows quite what to "do" with it (how many followers do you have with 0 pins and 0 likes?)
Pinterest is the Internet's virtual pinboard, with everyone tacking up--"pinning"--their interests. It's completely photo-based, lending itself to pretty photos of "things": things to buy, things to cook, places to visit. It looks like a shopping list for your dream shopping spree, which can leave people who aren't jazzed about finding the exact right lilac-and-honey-themed centerpiece for their table, or redoing the bathtub in spanish tile at a loss for how to use the site for themselves.
There is a joke somewhere in here about how Pinterest = Goop, and I will get back to you just as soon as I've worked out that punchline.