said by IowaCowboy:
What they could do to stop this is put a hardware based region lock on them so they can only be activated on a carrier in the country in which they were originally sold (even if unlocked) like the region locks on DVDs and Blu-ray Discs.
Another solution would be a cheaper version of the iPhone that operates on US frequencies only (GSM 850/1900 and CDMA 800/1900) instead of international (GSM 900/1800).
Can you imagine the consumer backlash? Never mind the international travelers.