After I wrote this post I wondered if I was over-reacting:
Ok, so I knew when I did the deal with Satan's pond-sucking scum that I should expect a shaft or two, but this one is so audacious.
I just noticed, in a very fine print amongst all the paper work of a new cell phone contract, that AT&T pays its rebates with an AT&T debit card.
AT&T has been sued over this practice...
I received my two cards ($50 each, one for each line of the family account), which are accepted "anywhere Visa debit cards are accepted", except you have to "tell the cashier" to "process the card as a credit transaction, not a debit transaction".
You need to activate the cards before use, by entering the number they're assigned to. AT&T tells me the number ends in 8. For both cards. Because both our phone numbers end in 8.
The cards expire in July of 2008, about three to four months after they came to us.
There are lots of complex rules about how to spend them. The only reasonable way to use them is to spend MORE than the card amount, then arrange with a flustered and irritated cashier (and their manager too?) to pay the residual through some other means.
Ok, so now I go to www.att.com/wirelessrebatecard to try to activate the cards. I'm redirected to https://www.888extramoney.net -- they're probably outsourced the scam. I'm asked to enter the "first 10 digits of your account number from your AT&T card". Well, I don't have an AT&T card, but I'll try the first 10 digits of the first VISA rebate card number -- since that might be tied to my phone number.
It turns out my theory is correct, from there I get a login screen that requests the entire card number and the last four digits of each cell number. I guess right on those and my cards are "activated". 
I could spit nails if I didn't have so many other battles to fight. I signed up with AT&T because of the #$!$#! iPhone. Compared to similar services from Sprint our family costs have gone up about 70% a month. Sprint, for all their many sins, didn't make me jump through these hoops.
In a just world AT&T would have to pay out billions for this kind of scam, but in this world George Bush is President, we have a Republican governor in Minnesota, and our state Attorney General has been neutered.
I just know some mid-level AT&T exec made SVP and a golden handshake when s/he came up with this scam to reduce rebate payments. I suppose it's unbecoming for me to to imagine her/his pending appointment in the eighth circle of hell ...
... The fraudulent—those guilty of deliberate, knowing evil—are located in a circle named Malebolge ("Evil Pockets"), divided into ten bolgie, or ditches of stone, with bridges spanning the ditches...
 It's not documented, but if you login this way you can see the record of card transactions and the residual balance.Update 12/29/08: One commenter suggested using the AT&T card to buy a gift card at a reputable retailer. Then you can use it when it suits you.
Update 3/6/09: As per a most appreciated comment AT&T has settled with the New York attorney general's office ...
A $2.63 million agreement with AT&T Mobility over a misleading and deceptive sales promotion involving rebate offers that were fulfilled with onerous and condition-laden rebate cards by the New York's Attorney General Andrew M. Cuomo.I sincerely hope Minnesota climbs on board.
AT&T is required to provide more than $2.63 million to consumers who received rebate cards from AT&T in fulfillment of its rebate offers on cellular phones and other wireless equipment and services.
This isn't AT&T's only mobile services scam. They're also shafting their customers with EDGE phones, effectively eliminating data services people have paid for by contract and phone purchase.
Update 4/20/09: Dilbert on mobile phone rebates. "Dude, we spent it before you left the store."