No matter how you choose to redeem the cards, this is income. The survey compnay is incorrect regarding the $600 rule. You must report all your income. They don't have to issue a reporting form if the amount is less than $600.
The purpose behind getting the income determines how it is reported. If this is a hobby, report it as other income. If you look at his as a job, you must report earnings of $400 or more on Schedule C. Otherwise, it is still hobby income.
