I've seen auto Amazon affiliate links on stack exchange sites and always thought it was a brilliant and non-bothersome way to monetize user generated content. With all this Pinterest/Skimlinks attention I realized that some people apparently don't think this is so brilliant, so I wondered what SE users thought about it and found this:

http://meta.stackoverflow.com/questions/26964/auto-inserting...

Looks like Jeff didn't "ask permission" beforehand but was explicit and open about the decision, and seemed to get a pretty positive reaction.