Welcome to the land of buyer's remorse. The Garland, Texas, warehouse is the size of two football fields and just about everything in it is something someone changed their mind about.

There are 400 truckloads a week: bikes, large appliances, clothing and electronics. All of it then goes up for sale or auction online, on sites like liquidation.com and secondipity.com.

Brian Johnson of Liquidity Services, a major player in the almost $400 billion business of flipping returns.

Reporter: Why don't the retailers resell it themselves?

Brian Johnson: A lot of it is box damage and if you go in and you want to pay full price at a retailer, you want it in pristine condition.

And handling returns themselves cuts into a store's profits.

Free shipping and liberal return policies have made it easy to get a refund for almost anything. Eleven percent of all purchases are returned.

Many stores track how much merchandise a customer returns, sometimes denying future returns based on their history.

Consumer advocates like Ed Mierzwinski of the U.S. Public Interest Research Group are concerned that data is increasingly being shared among retailers, creating a database of serial returners.

"I encourage any consumer who's been denied the right to return a product become some database they didn't know about said to the company-- 'Don't let him return the product'-- you should complain to the Federal Trade Commission," Mierzwinski said.

Best Buy discloses its tracking policy in fine print on the customers' receipt. Some stores don't.

The business of customer returns as the marketplace allows fickle shoppers the chance to change their minds.

You likely won't know if you've returned too much until a seller refuses to take it back.