Lots of people are doing this!
Many of them post their successes in the Trophy Case at the Free Lunch Room Forum. Just click the link below and you'll be able to browse the PayPal screenshots of a great many people who are all making money with this opportunity:
The Free Lunch Room Trophy Case
If you spend any length of time looking around on this forum, you'll quickly see that these are real people making money in this business and that it's not a scam in any way. If the pages I have provided under the Proof menu on the left don't convince you of this, then I don't think anything will.
Site sub-forums
Many freebie networks have sub-forums on FLR where users of the network discuss their experiences, and interact with the site support staff. Listed below are links to the sub-forums of some of the freebie sites I work with.