Social networks have become very beautiful walled gardens, but some of them remain more secluded and gated than others. Take for example Pinterest, whose treasure trove of user data remains almost like an unattainable holy grail for all but a select few of marketers. That changes today, however, as Pinterest announces the existence of API for third-party developers. But don't go dancing around yet, expecting some sort of Pinterest clients or whatnot to come gushing forth. It's still a somewhat exclusive party, just with a few more guests invited.