Naval Ravikant angel investor, Co-Founder AngelList and Venture Hacks and former entrepreneur
“[Ravikant] measure[s] four dimensions [in startups for AngelList]: Traction, Team, Social Proof and Product.” (AngelList is “a closed private social network [where] startups and angels [come] together.”)
“ social proof refers to who else is involved  as an investor and/or advisor. Which person has already given them the thumbs up is really important. If any one of those people who is associated [with] the company is phenomenal it [the startup] passes the filter [selection criteria] .
 Social proof is  powerful .  Get one great person to commit to your startup and you will have more control in raising your round. This is a tactic I have seen many startups use to start a bidding war or get the funding process rolling.” Naval Ravikant, Naval Ravikant and AngelList: The Match.com of Funding [Interview] by Fatema Yasmine, February 17, 2011; http://thenextweb.com/entrepreneur/2011/02/17/naval-ravikant-angellist-the-match-com-of-funding-interview/