Trust

[eBay founder] Pierre M. Omidyar… hit on the idea of building a flea market in cyberspace – where people could buy and sell anything to anybody. There was one snag, though. How could he persuade complete strangers to trust one another enough to hand over merchandise or cash without ever having met? Omidyar’s solution was to devise a system where buyers and sellers can rate their experiences with different traders… That provided the assurance people needed to feel comfortable trading with one another – and it helped Omidyar’s eBay become the largest person-to-person auction site on the Web.

Source: Green and Browder [1998].