Do cell phones impair airplane safety?


I must admit on most flights I’ve been on lately I’ve seen passengers whose sense of self importance, and tendency to defy rules, causes them to leave their phones on in flight, or turn them on before the plane has landed and the crew have advised it's alright to do so.  I’ve wondered, strapped into my seat and climbing thousands of feet into the air, is this guy next to me going to be the cause of a problem. How much credence is there in whether cell phones can impair flight safety? What's your take?
A new study by the International Air Transport Association (IATA) now shows there have been some 75 in-flight incidents in recent years (2003 to 2009) directly attributed to interference from a mobile signal, largely from mobile phones. Apparently there's still no definitive proof mobile phones were behind the cause of these incidents, but at least 26 of these incidents affected flight controls, autopilot and landing gear!
One such incident included the failure of the navigational equipment of a Boeing 737 in the US following takeoff, only to be reactivated after a passenger was told to turn off a sat-nav.
Our take is it's better to be safe than sorry, and perhaps if one person reading this will do as they're told on board a plane, flying might be a tad safer for us all. So next time you're in the air, do you think you might ask the person next to you to turn off their phone if they don't when the announcement is made to do so?