I signed up for inBubbleWrap.com a couple of weeks ago after reading the article about them in Publisher's Weekly.
The website features a new giveaway every day, usually a business book. Create an account, click on the button, and you are in the running for one of 25 free copies. Why are they doing it? Because publishers are paying them to. So far they've got at least ten publishers on the line.
The more I think about it, the more convinced I am that this is marketing gold. By giving away 25 free copies of the book, the site encourages hundreds of others to look at the book cover, read the copy about it, and click on a big button saying 'I Want One'. Maybe they win one, but probably they don't. If they don't, they've already completely bought in to the idea of wanting and owning the book in question.
I clicked and won, myself, already. I received my free book fairly quickly thereafter, a copy of Petra Rivoli's Travels of a T-Shirt in the Global Economy. It was, as promised, wrapped in bubble wrap.