Well...
I just spent a couple months asking friends and family to sign up for offers through my freeipods account. I had 7 people sign up and complete offers. I never got credit for 2 of the 7 but I did get 5. After I got credit for the 5th offer they said they were going to verify the accounts. After 3 days they put my account on hold and took 4 of my 5 approved offers away. They said that the accounts "appeared" to not be unique users...
I have no idea how they determined this, but I called several of my friends to see if they had been contacted which they had not been.
I really hope that they made some mistake. I emailed them to see what the deal was and am waiting for a response.
I will be sure to report back my results.