They probably disabled it because people were finding ways around the authentication process. Specifically ATT was checking the Agent Profile on the browser to see if it was running Mobile Safari. It was simply a matter of tweaking one's Browser Agent to emulate this and BAM. You are in. I never tried this but its all over the place for those who did.
I did this when T-Mobile was offering 3 free months of WIFI to Windows Vista users....change your Agent to Emulate IE 7 for Vista and create an account for 3 free months. My guess is ATT is not happy about this, DUH, and is now implementing an actual DBase that verifies through a proxy if you are running a cell # that has an iPhone. Which the logon initially suggests they were trying anyways...
*shrugs* Security through obscurity is always a crappy way of handling things. Someone will always figure out what you are pulling. In this case they did in all of 1 day.
I did this when T-Mobile was offering 3 free months of WIFI to Windows Vista users....change your Agent to Emulate IE 7 for Vista and create an account for 3 free months. My guess is ATT is not happy about this, DUH, and is now implementing an actual DBase that verifies through a proxy if you are running a cell # that has an iPhone. Which the logon initially suggests they were trying anyways...

*shrugs* Security through obscurity is always a crappy way of handling things. Someone will always figure out what you are pulling. In this case they did in all of 1 day.