American Express has a Return Protection line (1-800-297-8019) in which customers (I think limited to gold and platinum, tho not sure) can return products they're unhappy with for any reason within 90 days of purchase. I took advantage of this to exchange an iPod I just bought.
In any case, I just called to make sure my request was going through and was on hold for 15 mins. When the guy came on I asked if the long time was b/c of iPhone customers calling -- he said yes, and that it was the single busiest day they've had since he's worked in the office (I neglected to ask how long he had worked there). They've been getting flooded with calls, but iPhone customers are basically SOL, because the offer is limited to $300 per item. (Though it works great for folks like me who are just trading in iPods).
The American Express Blue credit card also features the 90-day product return protection. When a merchant will not take back a specific item, within 90 days, American Express will refund the purchase price up to $300 per item and a maximum of $1000 annually per credit card account.
TUAW reports that AMEX is "mulling" their Return Protection policy and that iPhone claims are being "handled on a case-by-case basis and that the refunds are not an official program or policy."