Sites which get frequent return usage and lots of user passion don't result in poor monetization: They get far more traffic, which compensates for the low CPM rate.
They "make it up in volume"? This is true for the big boys (FB, MySpace, etc). But is it true for all of the "sorta successful" sites out there that merely get a few million page views a month?
Equating monetization with advertising is a mistake.
There are lots of ways to make money -- if it's hard for your site to make money off ads, or if the overhead is too high, then it's probably worth looking at other means.
O rly? I agree that there are lots of ways to make money, but it's not as easy as it looks, especially for "social" sites. Facebook has a veritable army of geniuses, and they haven't figured out anything. What would YOU do with Facebook traffic?