A quick look at Amazon (Purple Cow, for example) shows an interesting gimmick. Answer a question about Amazon’s selection and you get a nickel paid to you.
What I like about this (other than the interesting use of Permission Marketing) is that they’re opening a fascinating door here. The goal, it seems to me, is not to teach you how many gameboy games they have (350) but to start an entire dialogue with you. Once they start giving you nickels, then they can have a dialogue about how to SPEND those nickels as well.
The other thing I like is how beautifully the UI works. It’s a click or two. That’s it. Beautiful.