From Mac Rumors:
A couple of readers have reported that AT&T hotspots are now offering free Wi-Fi access to iPhone users. Barnes and Noble, Starbucks and presumably AT&T’s 71,000 other Wi-fi hotspot locations are now offering iPhone users a custom portal to access free Wi-Fi. A special iPhone formatted page asks for your mobile phone number. Once entered, you can access the Wi-Fi access for free.
I can not see this lasting for long, I’m sure AT&T will fix this little hole. I first thought, oh this is going to be a complicated hack. Nope. Depresses me that AT&T made it that easy. Then on the other had.. is it part of some master plan to get more customers?