The search engine 50 Matches only crawls web sites that were bookmarked or voted for by people, in sites like del.icio.us, digg and reddit.

Enter social book marking. People save their bookmarks online (in sites like del.icio.us) and post links to their favorite sites (in sites like digg and reddit). In a way, people that use these sites act as smart agents and add to these big databases the most liked sites on the web. No company could compete with the man hours people put in saving and tagging their bookmarks. No algorithm could calculate site quality better than humans.