I'll text when I'm at a stop light, rarely when I'm driving.
I know someone who does constantly, and she's never been in a wreck... she has a Sidekick and can type like 80 wpm on it, and doesn't do it in traffic or on the highway (much

).
I think if you aren't glaring at your cellphone while texting, or steering with your knees because you have to use both hands, it's not much different than changing a CD or glancing at someone you're talking to.
I think some people's brains are wired to multitask and other people's are not... Those who don't pay enough attention while driving are going to be at a higher risk of being involved in an accident, regardless of what they're doing. Putting a cell phone in their hand just gives people an object to point to when they get into a wreck, instead of simply saying "they weren't paying attention".
They get into wrecks because they're changing a CD or talking to someone in the backseat or reaching for a french fry or talking on the phone or texting. I've done all of those things, as I'm sure many people do, and I've never been involved in a wreck.
The whole issue is overblown, IMO. If you aren't devoting enough attention to driving while texting, you probably weren't devoting enough attention to driving before texting.