"Pinterest is a success because it is qualitatively different and properly timed. It had proper resources to make it work well and scale at a time when the market was ready for it. The lesson to be learned here is that first to market is not as important as sometimes claimed. Most successful Internet platforms are second or third generation versions of an earlier idea."

Wists was Pinterest in 2005. Its founder talks about why Pinterest took off.

The side by side comparison of the two is eery, btw. They're the same service.