Paperspine runs on a model similar to Netflix's, but for books. For a monthly cost of $9.95 and up + postage, you can get two or more books out at a time. Their collection isn't huge -- 150,000 books -- but they do have a few books on advertising that I've been meaning to read forever, like the Confessions of the Advertising Man, and more good fiction than I'll ever have time for. Don't know if they have this entire social recommendation thing figured out, but it's a great idea for anyone who moves a lot and hates accumulating stuff. There's also Booksfree.com, a competing service with similar plans.