As of monday evening personal hotspot on iOS devices started to fail all over the US. Tuesday (yesterday) I began the Apple store / AT&T store dance. At first neither store acknowledged the problem. After 4 round trips between stores apple replaced the 4s which did not fix the problem. Last trip to AT&T and they did an in store assay and found that all store demo units with PH were also failing plus all instore reps who had iPhones with PH. A search shows this problem occurring all across the country. 2 problems: after updating to iOS 6 First: users loose the personal hotspot switch in settings and are asked to call AT&T to get it back after a network reset. Second: now that the switch is available...turning it to on claims it makes the phone discoverable but it doesnt broadcast its SID and you cant hard code a connection either. The fallback was always tethering with a cable but now network settings claims no cable or phone is not responding even though iTunes sees the phone (sync, backup, restore etc). And of course bluetooth sharing is broke too. As of this post Apple support claims they dont know what the problem is. AT&T claims they are aware of it, still think its an OS problem but not sure. Coincidence: AT&T made a change monday night to allow facetime over cellular for all plans and immediately personal hotspot breaks on ALL iPhones.