I saw two excellent example of the passive aggressive slam:
1.) Last night on Jeopardy! the contestants came out looking a little dressed down. The girl (Who was an art history graduate student and got one of the art history questions wrong. Ouch.) was dressed in slacks and a sweater and the two guys were both in dockers and button down shirts, one with a tie, one without. Alex came out and said, "Had I known it was casual day I wouldn't have worn a suit." Burn! The guy in the tie won.
2.) I was loitering in one of the non-fiction aisles at the library this morning (Musicophilia by Oliver Sacks - he's my smarty-pants crush. What? I'm 80!) and some guy was sitting at one of the carrels yakking away on his cell phone. I see out of the corner of my eye a concerned senior citizen walk up to him and I hear him slam something down on the top shelf of the carrel then walk away. When I walked passed him I saw that it was a sign that read, "Keep it low." and it had a cell phone with a line through it. You tell him Old Guy!