Ultimately, if the iPad takes off, the Kindle is in serious trouble. In order to maintain the complete, current selection of titles that is one of its device's great features, Amazon has to be willing to come to terms with publishers. Publishers, eyeing the prospect of millions of new iPad owners -- people who'd never have bought a Kindle, but are game to try out iBooks -- now feel more free to threaten to restrict Amazon's supply of e-books if their terms aren't met. If the iPad offers all (or nearly all) of the convenience of the Kindle, plus color (imagine the graphic novels!) on top of the ability to watch videos, surf the Web and check e-mail, many potential Kindle buyers will be happy to fork over the extra cash for an iPad instead. (If they're penny pinchers they probably wouldn't be thinking of buying a Kindle in the first place.) And without the potential profits from sales of Kindle e-readers to subsidize it, that standard $9.99 price tag is unlikely to last long. Without it, how much is the Kindle itself really worth?