My son was flying to EWR last Christmas and it was the beginning of that massive snowstorm. I knew he was in-flight but called his cell phone figuring I'd leave a message suggesting that he take the train into NYC, where he was visiting family, rather than risk getting stuck in a taxi for hours in a snowstorm. (He's 25 but hey, I'm his mother and I tend to micro-manage my own travel, too.) He answered the phone. Yes, they were in the air. I freaked out, gave him the message and rushed off the call before someone caught him and put him in plastic handcuffs. I think it was MDW and he seemed to think using the phone was permitted. Happily, the snowstorm hadn't started when he landed and he got a taxi with no problems.

I agree that I don't want a cabin full of people chattering on their cell phones- I've run into that in trains and it can be obnoxious. I remember to turn mine off 99% of the time and also disable the Wireless feature on my laptop and iPod Touch.