Mechanical Turk vs oDesk: My experiences by Panos Ipeirotis.
From the post:
A question that I receive often is how to structure tasks on Mechanical Turk for which it is necessary for the workers to pass training before doing the task. My common answer to most such question is that Mechanical Turk is not the ideal environment for such tasks: When training and frequent interaction is required, an employer is typically better off by using a site such as oDesk to hire people for the long term to do the job.
Like most things, whether you choose oDesk or Amazon’s Mechanical Turk, should not be an automatic or knee-jerk reaction.
Panos is an “academic-in-residence” with oDesk but even handedly points out when oDesk or Mechanical Turk would be the better choice. Depends on the task at hand and a number of other factors.
If you are considering using either service now or in the future, this is definitely an article you need to keep close at hand.