To an uneducated observer (that would be me and I cautiously assume most of the girls being compared on Facemash back then) girls were being evaluated on their physical appearance. That is not a noble pursuit.
I completely agree with you about the motives of the characters in the movie being ultimately for the movie. I think a lot of people in this discussion are reading way too much into Sorkin and Zuckerberg.
Anyone who seriously thinks Zuckerberg made facebook because he got dumped by a girl doesn't deserve acknowledgment. It was a mistake for Zuckerberg to even bring this up.