How can we know for certain that it's literally twice as hot? Chilli heat is measured in Scoville Heat Units. A jalapeno is 10,000 on the Scoville Scale, a Red Savina is about 500,000 which places the Bhut Jolokia at around 1,000,000.
At one million, it seems that the glamorous new showbiz oriented Bhut Jolokia (whose market value is predictably skyrocketing now that it is in the media spotlight) is more of a weapon or form of controlled abuse than an actually consumable vegetable but one woman, Indian of course, is gearing up to fly to London to create a record by slamming a whole heap of the mothers down.
She says she never really noticed how hot they were from eating them in the past, so she's prepared to fly to the UK to just go through the motions so she can get famous. Why doesn't she notice the heat? Probably because she's burnt her entire head empty and she now feels no pain.
Or anything else come to think of it.