I hate when a cute/good idea gets so common as to become annoying; everyone jumps on the band wagon :-) the smiley face/don't worry, be happy coming to mind? Right now, "Pay it forward" is starting to bug me, especially with the Progressive insurance ad guy taking its ideas (paying for the person behind you in line at a toll booth) and using them for commercial purposes. Anything that goes on too long will become a cliche and that is both good and bad.