[Quaestum]

To all those who are passport holders of countries being part of the US Visa Waiver Program: Remember that since the beginning of this year you'll render yourself ineligible for the Program once you travel to Iran (and a few other countries, see the link below). There are rumours on the net that this even applies for transit on Iranian airports without passing through immigration (entering the country). Current valid ESTAs are becoming invalid too.

Official statement for those who want to know more.