Ask HN: How do affiliate sales sites work and what % of sales do they make

I am thinking of creating an affiliate sales site (something like a daily deals aggregator) and I still pondering about a couple aspects of the business model and technology behind it. I hope someone can explain some details over the following:

1) I know that affiliate sales sites work on percentage from sales. I've been trying to find what percentage those site normally work on? I read somewhere that it is about 10% which sounds about right.

2) I've mulling over the technology behind those sites - one thing that I've found out already is that a small 1x1px image (with a source url, the url of the aggregator site) can be used on the last step of the checkout. Each request it polls, means a sale from the affiliate site. Which means that at the end of the month (or any other invoicing period) the aggregator site will have a pretty good idea of what amount has been sold from the affiliate.

One concern here, and maybe it is just paranoia kicking in, though: with this approach, I would have to rely on the honesty of the daily deals site. However, I've heard some stories before about sites turning off their affiliate link every x amount of orders.

Have you had any experience with building such sites? Or have you got any feedback/anwers/ideas on the points above? Please share

Much appreciated