depends on the person realli,
if its moronic based on the persons Lack of knowledge, than no time was spent, if its moronic in the "trying to be funny/witty," time was definately spent, than you guage the hilarity of the comment,to determine the amount of time, the funnier it is the less time was spent comming up with it. If it is a Truely moronic comment, too much time was spent, thus determining a waste of time.
how much time did you just waste coming up with this post? get a life!