What about all those gift cards offers advertising?

I've always wondered how websites can offer free gift cards, I see auctioned off for slightly below retail value on eBay. Are they for real? Is there a trick? "You can get gift cards from Best Buy and Wal-Mart? I know there is a trap, but I would like to know what you catch is.

They're real. I know people who have received material from it. However, there are totally free. All require sites to participate by accepting bids. Some of the offers must be signed for a year membership with Netflix. Either I fill out an application from American Express and approved. Either you must subscribe to a particular journal for a year. Ect. You end up spending money to get the items you get as a reward.

New Site Offering Free Things!