"Are advertisers getting enough performance out of Facebook ads to justify the expense?"
The answer could be Yes. It's also possible that many of the companies aren't managing their expenses well, and that they don't know (but still have enough cash, whether from stock market "play money" or VC (SV play money)).
There's no effective answer to the implied question, "How can we stop Facebook from being evil?" Even if the poisonous head of the snake is cut off, there is enough financial interest for remaining executives (and board) to continue along the same general path.
My answer is this: smart startups identify the key value features of Facebook and implement them independently. This is a long play, but it could work.
One example is how Facebook is used for communication and coordination of groups that share common interests. In this example, it's really just a little bit of communication features missing from meetup.com to replace this (and be better than what Facebook offers).