OK guys, calm down.

If you already have an iPad, you can get grandfathered in, and AT&T /can not/ legally change your plan once you're on it (read your terms and conditions, it's in there. slamming and cramming = bad). Grandfathered plans /will not/ be removed unless the feature actually gets removed from your account.. and you (or someone with access to your account.. don't give out your SSN and/or passcode) are the only one who can authorize that.. (and if it gets removed by accident and it WASN'T authorized.. well.. it /can/ be added back.. you just need to get a manager to override it).

Furthermore.. iPhone tethering has always been available.. it's called a jailbreak. It's not hard. Just google "spirit jailbreak" and in less than 10 minutes you'll have Cydia and can download the tethering app of your choice, whether AT&T likes it or not. Poof, iPhone tethering with unlimited data, no need to wait for Apple to release OS4 to the iPhone and then get put on a 2gb plan for the iPhone as well -- keep your iphone unlimited data forever if you want. 3

In fact, it doesn't even have to ring at all. With my Treo (which, of course, is GSM), it does that any time it does anything with the network. This includes incoming texts, checking email, or even just renegotiating with the nearest tower.