awesome. This topic has kept me busy almost entirely on its own for the past 5 or so years.
It's a split, I think... working off of experience from my friends (I'm a 19 yr old guy now, so we're just growing out of that stage... sample size is about 15 people). About 7/10 of them seriously subconsciously act as if they couldn't get hurt. Of course they would never say they were invincible, but they sure act like they are (it's the classic "well nothing bad has happened yet..." complex. The fact that they're still alive and racing means they haven't hit anything yet... so why would it now?)
2 of those 10 probably know they could get hurt, but risk it because they have confidence in their ability to drive fast. In all honesty, they probably do. The remaining 1/10 or so honestly don't care whether they live or die, so long as they're not injured so badly that they're permanently maimed. These are the guys who'll sit in the passenger seat of someone who drives crazy and stupid and choose not to wear a seat belt so that they're sure they'll die if hit. If they actually care about other people, they'll sooner drive off the road into an inanimate object than nail a living person, even though the resulting crash would be worse for them.
...what's up with all the rhetorical questions during conversation? (How often do you think "hey, how're you doing? How was your summer?" gets asked from someone who actually means it?)