I got 3 of them when I was in the States. It was interesting to see how the dollar bills travelled from one side of the country to the other. Come to think about it, I haven't received any updates in two years.
Its a totally brilliant idea indeed but I thought it was illegal to deface the dollar. Although, I might be thinking about the U.K., they have a law against it.
It is technically illegal in the U.S., but I haven't heard of it being enforced over this kind of deal.
#8 Is it legal to write on or mark currency? Where's George? does not encourage the defacement of U.S. Currency. The law defines 'illegal' defacement as defacement that renders bills unfit to be re-issued. For the legal details from the U.S. Bureau of Engraving and Printing, please Click Here http://www.bep.treas.gov/document.cfm/18/104
It's not illegal for defacing, as what I pointed out, it's illegal to advertise on U.S. currency. With all due respect, it's probably a bad idea to give out bad legal advice.