For many people involved in public relations and marketing, the notion that people would flock to sites comprised largely of images (no witty set-up lines, no pay-offs) may seem inexplicable. But the fact is that image-based sites like Pinterest and Instagram (along with video-based sites such as Viddy and SocialCam) are gaining an amazing amount of traction.
According to shareaholic, Pinterest now gets more traffic that Twitter or Bing (and almost as much as the two combined). It still pales in comparison to Google, and has a fifth of the traffic Facebook does. But its traffic is on par with Yahoo and StumbleUpon—and growing fast.