It's interesting to observe the highly varying amount that other cars will allow for merging. Merging onto the freeway during a busy day (maybe 35MPH traffic), I tried to merge and the car I was planning on going in front of moved up until their bumper was about a meter from the vehicle in front of them and leaned on their horn. "I technically have the right of way in this situation and by God, I won't yield it to you!"

This was a situation where there were about 40 cars merging onto the freeway and they mostly just do a fairly standard zipper merge.