In answering Learning Design for UI and Website Design I found myself linking to a lot of books at Amazon. Because it felt like an abuse I did not use my Amazon Associate link as a means to link to each book. However, I am not sure that everyone would have the same opinion that I do. Does the site actively prevent the use of affiliate program links or does it rely upon moderators and users to flag circumspect questions/answers?
Jeff has spoken... MSO Q# 2716
(In summary, no affiliate links in answers, even if the answer is otherwise good, useful, etc.)
I disagree with him, but this isn't my website.
As far as I know there is no filtering of affiliate programs. But out of personal opinion I would consider it very bad manner. SO isn't a place for you to generate money, especially by doing activities others do for free. Allowing this type of activity would also lead to excessive posting of links when it contributes no real value to the actual question.
Personally I would flag any links I see with referrals hidden inside because it just isn't necessary. If you want to place them in your personal profile, that's another story since users go there to find out more about you, but as a solution to a question it is unacceptable IMO.
Keep the dev team employed!
I wouldn't mind if there were a tag something like
which would translate to something like
with a stack-overflow referral.
I would say that posting affiliate links is easily considered spam. There's no automatic system that will prevent them being posted, but at the same time you could easily find yourself on the wrong end of the "flag as offensive" mechanism, as anyone with 15+ rep can (and likely will) flag it as spam, forcing its automatic removal and a -100 rep penalty.
So, in short, unless you're Jon Skeet, I wouldn't try it.
Ask yourself this: how would you feel if I edited your answer - which cited a book but didn't link to Amazon - and added my own affiliate link.
Is the effort I made to link to the book really worth the reward?
How 'bout this: what if I edited your answer, which already included your affiliate link, and changed it to my own... Keep in mind, this probably wouldn't show up in the revision history unless you actually viewed the source, which you wouldn't do if I made a bunch of other changes to mask it.
Now it's getting ugly, eh?
So my take on this is that at best it's trying to get paid for something the rest of us are doing for free, and at worst it's a slippery slope down to a morass of secret spamming. We should avoid it, unless/until the SO Team decides to implement Mark Harrison's suggestion.
I don't really have a problem with it, as long as you make it clear to all those reading the answer that you are doing so. Post a disclaimer or something, so that they are not taken by surprise - this is common courtesy.
I note that some affiliate schemes offer a benefit to the new customer, such as a discount.
The people offering the service or product benefit from knowing where their new customers come from (at the cost of the discount) and the new customer is incentivised to use a referral.
Are affiliate links still bad in this case?
I will acknowledge there is a privacy argument, but most of us already leave the Referrer: header in anyway. The sort of person who makes the effort to remove those is probably not the sort of person who would click on links with long id numbers on the end anyway.
(NOTE: I broadly agree with a_m0d. Its okay as long you clearly disclose its an affiliate link.)