He talks about "staged obligation", where you fool them into thinking the registration form is only two or three fields, and then, when they hit "submit", show them more fields. He claims that this gets a higher registration rate than showing them all the fields at once.

This is a great example of a "dollar auction". If you've never heard of them, here's the wikipedia explanation. http://en.wikipedia.org/wiki/Dollar_auction

Most of us get in a dollar auction whenever we are placed on hold for a long time. If you hang up, you lose your entire "investment" of the minutes you already spent on hold, so you keep holding.

I like this idea of applying dollar auctions to web site design. It had never occurred to me, even though I was very familiar with them.