I have actually received referral bonuses from Audible.com and ING for referring people to them. It helps if both parties receive something. Audible was giving both of us one free book, ING, gave me $10 and the other person $25 for signing up.
I didn't approach people, they were asking me about the services and if they were interested I'd tell them about the bonuses. To this day if someone refers me to something cool, I ask if I can help them get some kind of bonus for my referral.
As long as there are no high pressure tactics and both parties get something out of it, I'd have no problems trying to use it. Of course this would mean, in regards to Amazon, that I would get a free book and the other person would as well. Two books @ $20 total is less than the 10% affiliate program bonus. I think that would be a good deal for Amazon.