A bit stupid in my opinion that it renews automatically as Im sure there will be more than a handful of people who forget to cancel it and will get charged automatically.
Cue next months "news" reports about the guy who bought 3G service to test out his new iPad and though it was no-contract until he suddenly was charged for the following months service. D'oh! It'll be like the $1000 international roaming charges reports from the original iPhone.
Seriously -- It should be "opt-in" not "opt-out," but what fun for ATT would that be. I mean how many people will get charged for 3G service they didn't know renewed and won't notice it buried in their CC statement.