Obama and sarcasm

I don't quite get this John Dickerson column, which argues that Obama's use of sarcasm is this somehow new, and potentially suicidal, weapon. Hasn't Obama been this way since he started debating, ranging from "I look forward to you advising me Hillary" to that "Annie Oakley" riff? Hell, I think sarcasm is one of Obama's best weapons. Here is back in 2004 chin-checking Alan Keyes.