Correlation / compatability trust system

I want to market to people on media and social network sites like Criticker, everyonesacritick, and, as i hear Netflix. They use a system of finding people with as similar tastes as possible then aggregating those people's votes and spitting out the result. Just spamming wont work because i need to cozy up to users. Any ideas on how i should make the ratings?

Btw other trust improvements require money, real time or even revealing IRL id and i don't want to do any of this.