It's courteous to return the salute; expected, but I don't fault someone for not being a patriot or professional if they fail to salute back due to possible circumstances. For example, generals get saluted like it's going out of style. In a typical day they probably miss returning 10% of the salutes rendered them. So I don't fault BHO for not returning a salute, and that's from a guy who thinks he's got a ton of faults.