Valve has an annual peer view, it's described in the leaked Valve Employee Handbook.
Summary:
>There are no professional reviews by supervisors (because there are no supervisors). Instead, Valve uses a system of anonymous peer reviews, conducted once a year, where employees give their opinion of everyone they work with. Every Cabal is asked to rank the people they work with. No one ranks themselves. Results are delivered anonymously, and it’s up to the individual to decide what to do with the information. One concrete change that comes out of peer reviews is compensation adjustments. Valve goes out of its way to pay its people what they deserve, according to “who’s providing the most value at the company.”
Summary:
>There are no professional reviews by supervisors (because there are no supervisors). Instead, Valve uses a system of anonymous peer reviews, conducted once a year, where employees give their opinion of everyone they work with. Every Cabal is asked to rank the people they work with. No one ranks themselves. Results are delivered anonymously, and it’s up to the individual to decide what to do with the information. One concrete change that comes out of peer reviews is compensation adjustments. Valve goes out of its way to pay its people what they deserve, according to “who’s providing the most value at the company.”
http://www.forevergeek.com/2012/04/10-things-learned-from-va...