In some jurisdictions this would be a crime since the purpose is to prevent AT&T from operating its network, and thus your use of AT&T's network has exceeded what AT&T would consent to, and what you are licensed to do (it's sort of like a trespass theory). For example, I believe there is an appeals court case in Britain to that effect. I don't know if this is the law in the U.S., but I know of no such statute at the federal level (doesn't mean there isn't one), which is why I ask the poster to produce his authority for his contention.
Yes, Im sure AT&T would try to prosecute all its customers who use data that day. Lets all take our tinfoil hats off.
How would one prove that the way Im using my unlimited data plan that day is against the law or a procecutable crime?