At long last, Pinterest is launching an API that will allow pins to be embeddable across the web. The first partners for the API have already been announced, and include a host of big names: Zappos, Walmart, Disney, Nestle, Random House, and Hearst. It means that Pinterest will try to ramp up its traffic referral data – it’s current second after Facebook in that category – while making itself more useful to sites and brands to post pins and other social details across different networks. It also means more marketing to spend against these strong links between sites. It’s an important more, one that will likely see Pinterests’ already high relevancy only increase.