I would so do this to annoyingly loud phone users.
Have you ever been out in public and heard someone gabbing way too loudly on their cell phone? Of course you have. But Greg Benson of MediocreFilms — the same team that brought us Dancing Behind People at the Mall — came up with a brilliant way to shame these inconsiderate conversationalists. He parks himself beside the offender and pretends to be having his own phone conversation — but then begins answering the person beside him. He calls it “cell phone crashing” and the results are pretty hilarious.
Though Benson tests out the gag at the airport, you could really give it a whirl just about anywhere. Happy pranking!