Not every great idea should be copied. But thanks to NetFlix, which proved that DVDs could, indeed, be rented profitably by mail, people are now trying to rent anything and everything through the mail, with orders placed over the Internet. Purses, videogames, and now ... textbooks? Bookrenter.com is one such venue, claiming that it wants to "shift purchasing power back to students." It recently pitched Valleywag — always a dangerous sign, in and of itself — claiming to be the first textbook rental service on the Web. First, well, no. Secondly, any student who hasn't learned to scour eBay, Half.com, and a slew of online used-textbook sites deserves to be gouged by campus bookstores. Heck, most campus libraries have multiple copies of textbooks in their collections.