Easy said than done. For example, when Rogers closed the root for its version of the HTC Magic due to the E911 bug, the phone became unrootable for 5 months. It became rootable only when someone in Europe found, by chance, a new RUU for the phone to work.
So far, I haven't seen a successful rooting process for the Backflip. People are trying with the Sony Ericsson X10 but no successful so far.
Android phones are NOT Windows mobile phones. Windows mobile phones are easier to gain access. So, my suggestion to anyone who thinks somehow, someone will do a free service for them and root a phone, think again. The chances of successful root are higher with HTC phones, just because XDA people have more experience with them. For other manufacturers, it is up to the whims of whoever wants to tinker with the OS.
So, if you plan to buy a AT&T branded Androids phone just because of the subsidy, be prepare to live with whatever AT&T clipped the phone with.