...And few other reasons why people act/drive the way they do;
1) late for work, again...
2) late going home to make dinner...
3) In their little world other people drive too slow or don't know how to drive...
5) My car is faster than yours "Terret" Syndrome...
6) Soccer mom in a "Refrigerator on wheels" Van, late taking jr to practice...
7) Getting BJ and other drivers are watching.
...And the list goes on...I even saw a guy changing his clothes while driving in the highway WTF!

Some people just don't give a hoot about others when they drive. I Just keep cool, drive defensive and try to stay away from "Hot heads" on the road because you never know what they're going to do.
I think the real reason they cut you off is because they're pissed off they don't have a Hummer
