I was wondering if anyone knows if tethering is prorated on AT&T? For example, if you start tethering half-way through your billing cycle - will you only be charged $10 extra? Similarly, what happens if you cancel tethering half-way through? If tethering is prorated, it seems like a no-brainer to sign up for it the day you need it and then go back to the 2GB plan when you don't. Assuming you have either lost the unlimited data or you don't come close to reaching that cap, it really makes it seem like tethering is a good deal.