Balloons.What's the use? On the one hand they're synonymous with the good times – playfully batted around a dance floor, flanking a table of extravagant hors d'oeuvres or taped to the garden gate to symbolise there's a "party over here!" On the other they're a depressing reminder of your wretched old age, colourful orbs telling you that you should definitely be having more fun than you are ...