Surely that guy isn't selling ratings, as he's the client so he's the guy paying the low fees - presumably to get work (just cheap work), otherwise why would he spend $829 just to give contractors ratings. (Unless there's more going on than meets the eye, for example behind the scenes he's selling the chance to get a positive rating for more than he pays on the site.)

Yeah. Elance / oDesk aren't incentivized to prevent this behaviour. They want a site that looks busy, and full of "high-quality" / highly rated contractors.

They could easily allow for filters to weed, though instead they allow for details to be hidden.

Or just the final code or maybe have access to your servers or other assets - and without a full security check / wipe, you can't know if they created a way in - or they threaten to release your code publicly, or sell it, etc..

Just to balance the concept, usually people who have maintained good ratings for a long time, don't do this. I have worked for like 5-6 years at odesk part time, done around 40 jobs of varied sizes (hourly as well as fixed prices), never even once held back code or any thing, and barely once received some what negative feedback in which case i believe it was still my fault. So all sorts of people exist and work online. Those who have build reputations over years value it far more than the money, and an employer can easily trash the reputation with feedback. That being said employers from the western world are generally nice or may be it was just my experience :)

I don't understand how they would do this. On oDesk, both employer and employee only have the opportunity to rate one another after the work is completed and the project is closed.