I've sold BTCs and BTC-e coupon codes for Amazon GCs but only with people I trusted. I tend to trust the physical cards more than the digital codes, but I don't think those are a sure thing either. Here is the text directly from the Amazon gift card email that worries me (only if trading with untrusted):
4. Fraud.
Amazon.com will have the right to close customer accounts and
bill alternative forms of payment if a fraudulently obtained
Amazon.com Gift Card is redeemed and/or used to make purchases
on amazon.com or any of its affiliated websites set forth above.
So, basically the recipient is liable if the sender does a charge-back.