[martey]

This is covered in section 1.3 of AT&T's Wireless Customer Agreement: http://www.wireless.att.com/cell-phone-service/legal/index.j...

Basically, being able to get out of your contract without paying an ETF is only possible if they change the price of services to which you subscribe. Since tethering would not be a part of the data plans of the affected iPhone users, this would not apply.

[tseabrooks]

Also, after being enrolled you'd be able to call and/or log in to your account and simply have the tethering option removed without invoking the ETF...

[URSpider94]

... but by then, you'd be forever bumped off the unlimited data plan.