Why would you want to unlock your iPhone?
Because iphone is tied up with AT&T for 2 years you cannot
use anyother sim or operator. This is extremely inconvenient if you
roam often else you can switch sims to save money. Also it forces
people to switch to AT&T if you want to use iphone in the
process loosing your old number as well as your plan. Also people
doent want to stick with AT&T for two years. There is also a
strong market for iphones outside US so people unlock it to use in
whatever country or operator they want.
And you can unlock your iphone for free at