Originally Posted by Crashdamage
Browser ID, total data usage, other methods. If they really want to know, they can. Whether or not they bother to detect and enforce tethering bans or limits depends on the level of abuse and the carrier's attitude. T-Mobile is apparently fairly tolerant but has their limits. VZW will send Black OPS after you.
Ah, yes. I misinterpreted your point. You were saying they could. To that I definitely agree. If you are using lots of data (probably something like over 10 gigs in a month) I would bet you'll get looked into. I've got a 2GB plan and rarely go over. I do tether, but only once every few months. Like layovers in the Airport.