The key element, for me, is the idea of getting a sandwich board made up of one's book cover and walking around a convention with that--or just, you know, standing around on street corners. I mean, if you're going to want to tell people about your current release, might as well be up front about it, and just be right up in their face with a sandwich board.
Five Rivers has been experimenting with business-sized cards with bookcover and description on one side, download code and instructions on the other, as an easy way to carry around large number of copies rather than lugging a stack of print books to events. (In theory, stores could also display a large number of covers in a more limited space using these cards, but it's hard to see how the economics of that work out for the store/consumer when it is obviously cheaper to cut out the middle man.) So the sandwich board thing could work out great with a handful of the ebook cards. You stand on the corner, and if you catch someone's eye with the cover (front) or description (rear), you offer to sell them the ebook for $5 or whatever, collect the money, and hand over the business card download code. Easy-peasey!
Similarly, I see my kids jump up and run out of the house every time they hear the distinctive music of the ice cream truck. So an author with four or five "summer read" books could buy a used van, plaster cover posters on the side of the van, choose an appropriately themed but simple music loop, and drive slowly through suburbia looking for book buyers. I'd get off the couch and go buy a book if it came to my street!
Well, an author has to do something now that bookstore distribution is reduced to just the best seller racks....