[PaulHoule]

I've done some projects on Mechanical Turk (spent enough to get an account rep!) and I can definitely say that offers of money will bring in people who will (1) rip you off or (2) do the minimum work required to get paid.

The type (1)'s are easy to deal with because there are ways to check people's work. They just don't get paid. The type (2)'s are harder -- there's a population of Turks that I call Superturks that spend a lot of time Turking. If you make a histogram of how many HITs everybody did, they'll be the people who did the most.

The trouble with Superturks is that the quality of the work they do is worse than average, usually just good enough that you wouldn't feel comfortable rejecting their work. I know I could get better quality if I banned them, but I find it hard to do.

[sneak]

Reject mediocrity in all aspects of life. Spend money on good tools, and shun anyone who makes less-than-good tools.