This post doesn't contemplate one of the biggest problems on Odesk. The best of the "team" will perform the test. Then they put one of their low level team members on after the team leader passes the test.
The only way I have learned to work around the problem is to require use of the odesk time tracker with WEBCAM. Can't hide who is doing the work with the WEBCAM taking shots of the person. :)
Another way to handle this is to NOT hire teams, but hire independents. That's what I do on oDesk, to ensure the person you hired is the one doing the work.
Unfortunately it can't be avoided. I've always asked the question and most will say they work alone but then proceed to have team members do the work. It can become a big waste of time.
Actually Skype works quite well. As soon as candidate says "my mic is not working" and "camera is broken" you know that guy with name Ashish really does not exist - it is just imaginary person made by contracting agency.
However, odesk just recently started id verification process but I still relay on simple Skype calls and actually talk to person.
If it is agency I want to talk to manager/tech lead and actual programer.
The only way I have learned to work around the problem is to require use of the odesk time tracker with WEBCAM. Can't hide who is doing the work with the WEBCAM taking shots of the person. :)