The issue with gift cards -- and the reason why they can revoke them way after they are purchased -- is because people claim fraud. Just like my credit card could be stolen 6 months after I get it, so could the gift card. As such, they don't have a time limit on it, as they could be stolen at any time and they have no expiration.
What the scammers are doing is selling the cards, then claiming them as stolen. Just like if they were to sell you their credit card and then call their CC company to report it as stolen.
I initially thought the buyer of my card on Ebay may have been such a scammer - I followed all the rules on Ebay to protect against just such an occurrence. But Amazon has canceled all the gift cards that I had applied to my own personal account as well. So either (1) Amazon is being overzealous because of the one Ebay buyer doing something underhanded, or because (2) the bidders for BTC on Purse are scammers using stolen credit cards on a wide scale. I'll have to see how Amazon replies but I think the latter more likely now. (That said, I've also bought BTC on Purse (arbitraging the gift card funds I was gaining) so I know at least some Purse purchases are legit.)
I think Amazon's revoking of gift cards after the initial purchase is indefensible though. (And it makes a mockery of their statement on the gift card balance page, "Your balance will never expire." Yeah, but you never know when they'll cancel on you - so much for safe and secure!) Since the cards are bought and sold and given, you wind up with all kinds of innocent people down the line who get robbed by Amazon's policies.
Ironically, I'm in the same situation vis-a-vis my Ebay buyers as Amazon is to me. I could tell my two Ebay buyers "tough, I'm not going to be the bagholder here." But like me they were innocent buyers and should not be shortchanged because of a fraud committed by someone else. I briefly considered taking the hit to my 100% rep on my modestly active Ebay account, but it just isn't right.
The recent theft of Vericoin from Mintpal is another good case study to bring to bear here. I was a (minor) vericoin investor and supported the rollback of the blockchain to undo the theft. At first glance this seems directly analogous to what Amazon is doing. But here's the key difference: With vericoin there is a complete transaction history for the deleted blocks, and Mintpal publicly declared they would recompense everyone who lost funds because of the rollback.
This would be analogous to the credit card company or Amazon canceling the cards but paying those of us back who were not the guilty parties. I don't see that happening here, so it's wrong for Amazon to be shifting the burden of the thefts from themselves or the credit card companies onto a broad and innocent section of their customer base.
Do they understand the PR disaster they are potentially making? Think I'll be silent about it on Facebook and so forth if they wind up canceling $915 in my gift cards? (And there's more - come to think of it I have to warn my mom about a $50 birthday Amazon card I sent her.... this is ridiculous!) Trying to close the barn door after the horse was stolen is not the right thing to do here.
The irony is this whole mess could have been avoided by adopting bitcoin. (Merchants have nothing to fear from bitcoin scams so long as they keep their own account secure, making situations like this impossible.) I'm reminding Amazon of that.... repeatedly.
UPDATE A response from Amazon says that the gift card held by the Ebay buyer was already redeemed. This is option (1) in my post above, not (2) as I was inclined to think. So it appears I've got a run-of-the-mill Ebay scammer to deal with, most likely. I'm going to ask Amazon about their policy for canceling gift cards post-purchase to see if I can get some clarity here. This does raise my hopes somewhat. Amazon will still need to explain why all my gift cards deposited in my own account are zeroed out though.
UPDATE 2 Further communications between Amazon and my Ebay buyer show that Amazon was misleading - the Ebay buyer does NOT appear to be a bad actor. It is Amazon that is the problem - scenario #2 in my post above. I'm going to be publishing my investigation/complaint as "An Open Letter to Amazon.com" here on Bitcointalk when I've compiled it, as the normal communication channels with Amazon are not working for a case of this complexity.