I know lots of people use Bankdirect to earn the free mileage bonuses, but I thought I would share my math on why it makes sense to actually keep money there... Let's say that right now you get 1.5% APR from your US bank account (btw... PM me if you do with details ). If you put $2500 in your account and left it there for five years, you would have $2693 pre-tax. If you were at a 25% effective tax bracket, you would have $2652 net of taxes. If you put that same $2500 in Bankdirect, you would have earned 15,000 miles over the five years. 15,000 miles at a cost of $152 is $0.01/mile. Hard to beat that! ** EDIT ** Potential Fees I did the math off of $2,500 because below that there are monthly fees. If you can't keep $2,500 in your account, this isn't the account for you. There are also fees for accounts kept open for too short a time. Their full list of ancillary fees is listed here. Thanks to Bluto and Biu for their suggested updates.