Soldato
Thats a fair point but a lot people enjoy smoking even though they know its a filthy habit (like me). As for shortening life and getting cancer... I'd rather enjoy here and now, never know when your gona get hit down by a car... which lets face it, they kill a lot of people but people still drive. Anyway its a fair point but you can add the risk factor to pretty much anything.
According to this guy http://forums.overclockers.co.uk/showthread.php?t=18545971 we can predict when people will be hit by a car