"Yes. One time he didn't. It was at an event in Indianola Iowa when Obama was photographed as the sole person on the platform not holding his hand over his heart while the National Anthem was being played. It is widely considered appropriate to stand in reverence of the flag even when one does not put ones hand over ones heart, which is what Senator Obama was doing at the event.
The implication, obviously, is that failing to display the proper hand-over-heart etiquette proves Obama is unpatriotic and therefore unfit to hold the office of president. Some have even speculated that it was an intentional gesture of dissent on the candidate's part, to which an Obama spokesperson replied on Inside Edition, "Sometimes he does, sometimes he doesn't [put his hand on his heart]. In no way was he making any sort of statement, and any suggestion to the contrary is ridiculous."