Pinterest currently drives 7.1 percent of Web traffic, second only to Facebook (21.3 percent), and is miles ahead of other social sites. Investing now is a long-term play for growth. After all, the company has announced its long-awaited “buy” button today, and revealed that it will be launching a video pins strategy in June, making them another avenue for video distribution and discovery. And with a new multi-image ad unit on the way, there are more and more opportunities for publishers to turn pinners into shoppers.