This picture shows what happens when someone stops at the end of an entrance ramp that you aren't supposed to stop on. It's hard to tell from the picture, but there is plenty of runoff space at the end of that ramp to keep moving and find a gap in traffic... but instead, the person in the black Accord decided to stop instead, even though traffic was not very heavy at that time. As a result, there were cars backed almost all the way up the ramp.

So in case it wasn't already obvious, stopping at the end of an entrance ramp is BAD. Not only will it make it harder for you to merge into traffic, but it'll also cause unnecessary headaches for both the people you're trying to merge with and the people behind you, and puts you at high risk for being rear-ended.

Of course, there are exceptions to this - especially here in the metro NY area, where some of the "high-speed" entrances are sorely outdated and downright dangerous. On those, it's often necessary to stop to avoid causing an accident, simply because they aren't designed with proper acceleration space. Because of this, I am compiling a dangerous exits list that will go live sometime in the near future.