No more of less ridiculous than the rule against electronic devices below 10,000ft on passenger jets. I got screamed at because I was taking a pic with a tiny P&S at about 7000ft while passing by Chicago. Like my tiny camera was going to cause the plane to crash or something.
Yeah, I got into a small argument/discussion with a flight attendant about that once because I got permission from another attendant and this one [MOD EDIT - profanity removed] was telling me I cant use my camera for some ridicuolous reason. It doesn't transmit ANY wireless signal and I believe myth-busters proved the whole cell phone thing to be false anyway. I know friends who have used their data network on a plane before when they had signal and they lived to talk about it :P
Back on the battery thing though, I think that new rule is complete crap since it only effects the USPS and outgoing mail. No wonder they are loosing money and going under. We need a mail system like Europe. My friend in Sweden was telling me that overnight to 2 day delivery was the standard mail there. Nothing special or over priced.