The fact that CO hasn't discontinued the program yet suggests to me that it is a money maker (either on the $25 annual fee, the CC tie-in, by driving bookings through CO.com, or a combo of all those factors). You don't think UA might adopt the program if it is profitable.

I doubt it requires much overhead to maintain/administer the program... just a few lines of code (already exists on the CO end) and some 1s and 0s representing balances stored on a server somewhere.

UA regularly has 10%/15%/20% promo codes for discounts off of certain fares (which CO usually doesn't do). A $5 discount (which is what a TravelBank credit really is) would often be less than 10/15/20/etc. UA could discontinue such discounts, and most people would feel (though not supported by reality) that they were getting more in return through a tangible $5 credit. The power of marketing. :-: