Thats it hey. Its the 'unknown' factor. You dont know what is in their car, what they are on, why they cut you off, who they are etc. He could have just robbed a bank, killed the guard and not give a rats if your the next victim.
Seriously dude, say on your average 30min trip, you could let 5 cars in, the MAXIUM that is going to add to your trip is 1min if its heavy traffic.
But in regards to the keying thing, I hope the barstards get real bad hurt, by say an angry bull shark or something. Keying reallly gets on my nerves, if they push hard enough its got to be the hardest thing to fix up properly.