So if I use TetherMe or MyWi just to connect to my iPad mini is AT&T really going to notice? I don't imagine there will be a huge data spike since I am not connecting to a laptop.
The important point is this: No one (on here anyway) knows for sure how the carriers detect tethering. It's likely however that it is not just data usage.
Having said that, the carriers vary greatly in enforcement, even within their own customer base.
I have been told by one carrier exec that basically 'All animals are equal, but some animals are more equal than others' when it comes to enforcing this. i.e. they may notice you're doing it but not care because you're a good customer.