I was on a flight early last year from LAS back to JFK when about halfway through something broke out with a drunk passenger. I don't know what exactly happened but for the first time ever I saw a sky marshal go into "action". I use quotes because quite honestly he didn't seem to know what to do and looked as clueless as any of us. The flight attendants took more action in calming this man down than the sky marshal did. He mostly just stood there with his hand extended out towards the man and kept warning him that he would be detained if he didn't sit down. The drunk guy couldn't care less.

They are just another part of the entire homeland theater on display with respect to flying.