In a country where apparently 18% of the people believe erroneously that their president is a Muslim, they would probably be better advised to concentrate on reading rather than burning books.
In principle I much prefer the US's First Amendment in contrast to our own archaic blasphemy laws in the UK - I see no reason at all why religion should be singled out for exception from ridicule or abuse.
The notion of a text being the product of some kind of divine dictation is ludicrous. In fact even the most hard-line headbanging fundamentalists of any persuasion at some point have to contextualize their holy books on linguistic or historical grounds. And as soon as they do so, they logically open the door to the subversive idea that their religion might just be 'man-made'.
But the problem with burning the Koran - or any other kind of book - is not so much fear that it offends its followers as the fact that it tends to identify the burners as ignorant fuck-wits who lack the ability to tackle it intellectually. Or just xenophobic bigots. Although I suspect though that it was not this that has now inhibited the Pastor Terry Jones from holding a Koran-burning at his Florida church to marked the 9/11 anniversary.
Personally I tend to think there is something in general sacred about any book- which is why our house is groaning under the weight of a lifetime of never throwing any away. I certainly wouldn't burn anything - not even Mein Kampf .... or a Jeffrey Archer.