my 2 cents on it...
1>. The Ad com takes it as a failure to follow directions.
2>. It's unfair on the other applicants as most other applicants keep within the word count and it's fairly obvious that you can get more "juice" in your essays with a slightly larger word count.
You can however exceed to within 10% of maximum word count but dont exceed it preferably..Although you wont be rejected for exceeding the word count, it is looked down upon.