What About Bob makes him funny?

I think humor is the result of unexpected incongruities in an otherwise predictable series of events.  For example, what makes a joke funny is usually its punchline, and that joke is only funny if its punchline is unexpected but still makes sense in context of the joke. 
What makes the movie What about Bob funny is Bob's ability to screw over Doctor Leo Martin over and over again in drastic and unexpected ways.  Each time Bob infuriates Dr. Martin, it was exponentially worse that the last time, and most importantly, was unpredictable.  Of course, humor is subjective, and what one person finds funny, another will not.  For example, while I can acknowledge that some would find What About Bob funny, it just makes me uncomfortable.  On a larger scale, there exists a fine line that separates humor from taboo, but that line lies in a different place for every individual.