How Do they Do it?

You know the email submit sites most of which will offer a gift card or some such if you complete a number of offers. I was just looking through one such offer on market leverage. Anyway, after you submit your email, you get to a page that tell you to complete 2 slver offers, I think 4 gold and 6 platinum.

Here is a link to their gold offers: http://www.betternutritionguide.com/...ates.php?pop=n (might display somethign different if you remove the /affiliate.php? part)

So, most of their offers seem to be basically cpa offers (or the same idea) and many if not most are trial program with continuity.

I have two questions on this. 1) How exactly does this work? How do they track it if you actually complete an offer once you click from their site to the "sponsor" site and 2) If some poor chap actually completes all the required offers, and then since he didn't cancel (I bet most don't) gets hit with a charge for something along 1,000$ (figure 10 trial offers.. lol) I would assume they'd get really, really upset.

So how do those sites stay in business? Good disclaimers I suppose, but still.