It is a liberating feeling to be unreachable the whole day, you should all try it!
Entirely agree,
fortuna76, if your colleagues/friends/family can't cope without speaking to you for 24 hours there's something awry somewhere! However (as I've said on here numerous times before, sorry!) every flight with more than 50 pax will (almost certainly) have at least one active mobile on board, if only by accident. Since we observe few planes falling from the sky, I think we can conclude that the risks are quite small.
To eliminate the risk, you'd have to screen all baggage and travellers for active mobiles, which is not difficult but costly and time consuming. I'm waiting for the first on-board cell to fail and see what happens as umpteen mobiles all try to contact the next nearest base station 35,000 feet below ...