Citibank's new prepaid card might have some mileage/rewards earning potential for those with Citi credit cards. I found information about the new Citi "Cash Card" at http://www.cashcard.citicards.com/

Some highlights:
"Annual Fee: $25.00
Load Fee: $1.50 - per load money transaction (waived when money is loaded to the CitiŪ Cash Card from a Citi credit/debit card or a CitibankŪ checking/savings account.)
Cash Withdrawal Fee: $1.50 - for each cash withdrawal at ATMs and bank tellers (Waived for cash withdrawals at Citibank ATMs.)

The minimum amount that can be loaded at the point of initial load is $10 dollars. The minimum load value amount going forward is $10.00 and the maximum is $1,000.00 within any 14 day period.

Each responsible party (Master Accountholder) will be limited to a maximum of 5 accounts."

So it looks like the most you could run through it in a year would be ~$26,000. If you use a Citibank card to fund the account and withdraw cash from Citibank ATMs, it looks like the only charges you'd pay would be the $25 annual fee. (This is assuming that the "loads" are treated as purchases by Citibank cards, similar to c2it, and not cash advances.) If one were really ambitious, one could get close to $130,000 of annual spending by opening the maximum number of Citi Cash Card accounts (5). That's a lot of time at the ATM, however, and given c2it's predilection for closing accounts, I'm not sure they'd let you get that far.

(BTW, this thread might be better placed in the Visa/MC forum.)