I remember right after 9-11 when Bush said that the individuals who attacked us had blasphemed Islam. He was, of course, trying to make the point that he understood that such actions are not an expression of normal Moslem belief. But I remember wondering whether it was appropriate for someone who is an outsider to a particular religion to decide that someone is a blasphemer.
On the other hand, when I heard a description on This American Life (start listening at the 23:30 mark) of things that are being done to prisoners at Guantanamo, I knew that it was time to call blasphemy. There's a good chance that the person who kissed the cross and said the torture was a gift from Jesus identifies himself or herself as a Christian. For any professed Christians who have invoked the name of God as a part of torture, you are being officially called out by an obscure Christian cleric (I really am a licensed minister, everybody) as a blasphemer. Just doing my job.