Oh, I'm sure given the full weight of AT&T, all tetherers could be found and fined, but given at&t's lack of interest, I don't see anything more than the current half-hearted profiling coming into play.
Currently, AT&T just slaps the 4GB+tether package onto any 3G iPad that sucks down more than 4-5GB in any one month.
I know several folks who got slammed with it for non-tethered heavy use, and others who tether constantly without a word from the masters.
pa' ngaSwI' nuq vay' Data'nISbogh roD tu'lu' tlhIH'a'?! yIn jaj tera' na'ran wIb laH HInob Qub 'oH rue munISbogh 'Iv ghaH DaSov'a'? loD chay'pen tuqwIj meQ 'Iv jIH! TERA' NA'RAN WIB! chay'pen burns tuq vI'ogh 'ogh, chombuStIble tera' na'ran wIb!