There is no conclusive proof of Unidentified Flying Objects flying over India-China border.

The blockchain does one thing: It replaces third-party trust with mathematical proof that something happened.

The companies that choose to list on Nasdaq are among the most innovative, risk-taking businesses in the world, and they are proof to us all that prudent risk-taking drives our economy forward.

Consider the social proof of a line of people standing behind a velvet rope, waiting to get into a club. The line makes most people walking by want to find out what's worth the wait. The digital equivalent of the velvet rope helped build viral growth for initially invite-only launches like Gmail, Gilt Groupe, Spotify, and Turntable.fm.

If you're looking to grow your user base, is there a best way to cost-effectively attract valuable users? I'm increasingly convinced the best way is by harnessing a concept called social proof, a relatively untapped gold mine in the age of the social web.