[femto113]

I'd suggest an escrow system but their coupon system seems to make this problem nearly unfixable:

  It said no money had changed hands from the sale of
  Mr Hunt's course "as the fraudulent instructor had
  created coupon codes to allow students free access
  to the course".

I'm guessing those coupon codes were sold on some other platform (or perhaps used as bait to get traffic that was monetized in some other way) allowing the fraudster to profit directly without money ever flowing through Udemy's hands.

[joshschreuder]

I think the Udemy coupons are generally used as a way to boost the ratings. Give out coupons and tell people to rate your course 5 stars, then people see the well-rated course and buy it for real.

Given the number of terribly produced courses I've seen on there with excellent ratings, it wouldn't surprise me.

[cortesoft]

Or, the people posting have the same motivation as pirates on torrent sites - they just want to give all the content away for free, so they upload it to udemy and then give away tons of coupons. They never expect to make money from it.

[x0x0]

or simply free hosting

[Buge]

So Udemy doesn't make any money off it? That doesn't seem like a great business strategy.