I have always argued for engaging with technology as conscious human beings and dispensing with technologies that take that agency away. Facebook is just such a technology. It does things on our behalf when we’re not even there. It actively misrepresents us to our friends, and worse misrepresents those who have befriended us to still others.
This, more than the typical advertising/privacy concerns, is the thing that really bothers me about Facebook. Over the course of its existence, the way we interact with Facebook has become increasingly disconnected from the way our activities are presented to the network. I remember John Gruber saying that one of the reasons he instantly liked Twitter was how simple and obvious its mechanism was: he typed in the text box and everyone who followed him saw it; when people he followed typed, he saw it. By contrast, Facebook is an opaque algorithmic beast, and I’ve never felt at all in control of how it presents me to the world.