One papercut is a nuisance 100 million is another thing altogether.
http://news.cnet.com/bank-robber-hires-decoys-on-craigslist-...
It's also far less traceable. Instead of paying 50,000 people to stand in line outside of Palm, you're paying 50 people each to stand in line outside of 1000 different local businesses, whose only connection is that they happen to be next to a Palm store. A just-as-plausible explanation is that you're organizing a "buy local!" protest that day.
You could also pay people on Amazon Mechanical Turk to pay turkers to stand in line, making things even harder to track. Now instead of one guy paying 50 people each to stand in front of 1000 different locations, you have 50 guys, each one of which is paying people to stand outside Subway, or McDonalds, or Verizon, or the corner bookstore, or whatever happens to be next to that Palm store.
So?
People are not going to go out of their way, or risk jail time, for $1.00/task. You'd need to pony up a lot more money (like, I'm guessing, 100's of thousands of dollars) to get enough people to violate basic principles on a large enough scale for this to create some sort of shift.
After all, for someone to get anywhere doing ill with MTurk the request must be seen by people.
I do think it is very interesting to see the faces behind Mechanical Turk.
On top of the seeming additional liability Amazon would be inflicting on themselves, I can't see any upside to Amazon going to extra lengths. It would anger project creators to have to wait for human approval for every project, it would likely reduce the number of jobs underway at any given time (making it less profitable for them and less lucrative a market for service providers), and it would increase the expense of running the market at human scale rather than computer scale (even if they somehow figured out how to use Mechanical Turk itself to provide the vetting). In short, vetting jobs would be a recipe for a fiery death for Mechanical Turk.
Perhaps considerations of aiding and abetting prostitution, kidnapping and drug-dealing would enter if the job requests were entirely unvetted?
Uh, and I think India has labor laws too.