[robsta]

Eh, highly doubtful. I have tethered on AT&T with my old Wizard and Samsung Blackjack with no consequences. I used to use my Blackjack for online gaming as well. Currently, I'm on Sprint tethering with a Touch Diamond. I'm a high data user, I use about 1.5-3 GBs per month.

However, my usage never really changed, I started using that much since my first month with both carriers. I guess if you used like 500 MBs a month and suddenly it jumped up to 3 GBs a month they might ask questions.

It is possible for them to see if the data requested is coming from a PC or mobile phone, but its involves examining the data coming through, packet by packet, very time consuming, and definitely not cost effective. I wonder what they would do if they caught you anyways, they would probably give you a warning first.