I've carried my cell while hunting for the last 3-4 years, meaning I've survived without one for 30+. I leave it switched off for obvious reasons. I'd say that a good 90% of the time I have no signal. But it would never occur to me to leave it home. Like any other tool there are situations where it will be useless, but if I need it I'd rather have that extra 10% than not. Certaintly on a scout trip the leader(s) at least should carry one. I think it would be borderline negligence not to.