The reason it's restricted is because ... Drum roll... There is no good reason . I'm under the assumption that once a device has a 3G chip in it that is being billed under AT&T then AT&T assigns a phone number to it. The same is true for any wireless laptop card that AT&T offers, ( I have one) it has a phone number. On verizons wireless cards you have the option of SMS via the wireless card even though you can't receive calls, because it has a phone number, the SMS option is available. So, the bottom line is that AT&T could easily allow SMS transmissions to go back and for to the 3G sim card, and bill you for it if they so desired. Apple could, on their end, port the iPhone SMS app to the iPad to allow this functionality. Why don't they both collectively enable it???? Because they just casually decided not to. Meanwhile I would imagine a majority if soon to be iPad 3G owners would at least be comforted with the fact that the option was there if they wanted to pay for it.