Here's a recent posting on "how the web makes money," focusing on the on-line gaming community.
The bottom line: successful game sites rely too much on questionable vendors.
Game players like to acquire game currency to improve their experience, especially as new players. They can often either buy game money or they can "earn" it by clicking allegedly "free" links. These sometimes give them game currency for free, but too-often involve scams.
While this Cryptosmith site pays for itself through consulting leads, I've always been interested in more direct methods (described here)
. I think it's fair to collect a commission if I directly encourage someone to buy something, and I gave them the link to buy it. The jury is still out on whether this is worth the effort of constructing the links. I'm also curious as to whether this opens me up to various forms of fraud.
When I do
provide links with commissions, I limit myself to links that I might use myself. I hope that that provides adequate quality control for my visitors.