A lot of apps, especially games, you can finish using within 7 days (or even 1 day, plenty of iPhone games do not have over, say, 12 hours of gameplay).
I was never made to feel guilty about borrowing those books from the city library, returning them two weeks later and never buying them. When did the standard change?
It will be very interesting to see how they handle ebooks. I'd be surprised if the publishers didn't enforce scarcity.