I just want to clarify for a few of you that still seem to believe accounts are flagged for tethering by the amount of data being used. This idea is simply false. It doesn't matter if you tether a little or a lot--you are still tethering. So, to resolve a myth, do not think that by cutting back on your tethering time decreases the likely hood of your account being flagged.
Also, from account that I've read, AT&T customers who have jailbroke their devices and used PDAnet with the "hide" feature enabled have also received emails and texts messages from AT&T notifying the customer of their awareness of their actions, and some have actually been forced into the tethering plan as a result. It appears that, as of now, there is no way around it; so tether at your own risk. Don't ignore all the confirmatory evidence.
I may be wrong, but it seems that the answer may lay in software for the tethered device that tricks it into sending or seemingly sending information as if it were your actual iPhone.
Well I've never received a text from AT&T using PdaNET's Stealth Mode. Of course I've never used anything besides Stealth Mode.