Sherlock Steve has had some pretty good points when talking about texting while driving. The recent Washington Post article, Textwalkers: Do They Need A Heads-Up? talks about things like this including textwalking. There's even mention of laws being passed related to texting.
Folks, put down your pagers and just walk normally. You do not want to be in NYC or other city when you fall down the steps to a subway station while deep in a text convo... Same with driving, just pull over for a bit. It's not worth it being flattened by a speeding bus, truck, or train. I've seen the pics and they ain't pretty.