I think the reason behind people assuming that "happy=crap" is because, for the most part, memories that bring about feelings of gloom or sadness tend to affect us longer than do moments of happiness & glee.
Winning a million dollars in the lottery will make you happy, but the feeling will not affect you as long, or as strongly, as the memory of a loved one passing.
I believe that feelings of depression are connected to a larger part of our mental functionality than happiness is...but I'm not gonna really get into it because it's 1:30 and I need sleep.
Anyway, you'd have to take into effect our surroundings, chemistry, etc to get a real answer to this question. Actually that'd give you the REASON for the answer...but ehh whatever...
later
c-lo
P.S. Enjoyed the post, SilentKnight!