MAP = Minimum Advertised Pricing.
I work with it all the time. It's because you've got professional full service places who promote products, have trained staff, and honor warranties. They have to sell at reasonable margins to stay in business. But they typically yield considerably happier customers. Best Buy is a good example. I know most of us techies don't think very highly of them, but lets face it, if there's a problem they'll usually take care of it.
Then you've got a guy with a pretty website, working out of his home, using his garage as a warehouse. He can sell at 5% margins with zero knowledge or service and steal LOTS of business away simply by having the lowest price on Google shopping. If something goes wrong, you're screwed. God help you if you want a return or exchange.
That's why MAP exists. Manufacturers WANT their equipment sold by full service places, so they establish a price that you cannot advertise below. In the case of the Xoom that is $799.
The good news is that dealers are welcome to sell at any price they want. They just can't advertise it. And furthermore very quickly there are idiots who will violate MAP on Friday afternoon, rake in sales all weekend, and get a stern warning on Monday morning.
Trust me, unless you're hideously impatient, you won't be paying $799 for your Xoom.