jumbled risk analysis thoughts

I guess a study came out recently, because I've now seen 'texting while driving make you 21 times more likely to get into a wreck' quoted several times recently. And, yes, I have no doubt texting while driving is quite stupid. But that phrasing bugs me a lot, because it implies an arbitrary threshold. (And nothing annoys computer scientists like arbitrary thresholds!)

You know what else makes you 21 times more likely to get into a wreck? Driving 21 times more. Sending a text takes, what, a minute? So in that minute you're exposing yourself to the same risk as in the next 21 minutes of driving. Of course, no one would ever imply you shouldn't drive for 21 minutes. Driving is dangerous, period. It's one of the most dangerous things most people ever do. You can't ignore that, and pretend that risk doesn't exist. How many people are horrified at the thought of riding a motorcycle occasionally, but buy a house out in the exurbs which forces them to drive 10+ hours a week?

The texting stat as reported annoys me because it implies that the risk taken while driving is perfectly acceptable, but anything more than that is absolutely irrational. It implies that there is 'safe' and 'unsafe', instead of a continuous range of risk which everyone has to evaluate themselves.