I just read this bit about the new PayPal Mobile, and it sounds really cool.
Like any new technology of this nature, what matters less is the technology around it, and more the chicken-and-egg problem of getting people to sign up for an account when there are no retailers using it, and retailers to start using it even though there are no people signed up. I’d love to see something like this take off though. Eventually a cell-phone based payment system could evolve to replace credit cards, and could probably be designed to be faster and more secure. This system is comparitively clunky, but would be a nice first step.
Plus if every print ad could effectively be a storefront, that might make print ads more profitable, which presumably would mean newspapers/magazines could charge more for them, and require less of them. Some magazines these days have 3-4 pages of ads before you even get to the table of contents.