At least that's what the connection appears to be. I jailbroke my phone so I could tether it. Everything seemed to work fine but, a couple hours later, I got a low battery warning. It was surprising because the phone was plugged into the AC adapter. I figure maybe the adapter's defective (first time I'd used it) so I plugged it into a Mac. But the battery was still discharging. Skipping over a lot of troubleshooting, I think I've narrowed it down to the fact that I'd left a telnet session open to a remote system. It seems that every time a 3G connection is active, charging stops. When the 3G connection closes, charging resumes. I can actually watch it happen (in slow motion). And, with the phone plugged into the AC adapter, I can feel the adapter cool off when connections are kept open and warm up when they're closed. If my suspicion is correct, it would seem that Apple designed the phone to do this in order to keep a handle on the amount of data that a user can get through the phone. Can't change the battery + can't charge when online = 2-3 hours of steady 3G use per charge cycle. BTW, if I turn off 3G, maintaining an active EDGE connection does not appear to interfere with charging.