Yes, privacy is important. However, the only information that I've ever put on Facebook is information that I'd want everyone else to know. That's why I have a Facebook; to give people who don't know me an idea of who I am and what I'm like, and get a little bit of personal branding out there. For instance, there's at least one little portion of my life that I don't want to be broadcast out to everyone, so it's conspicuously missing.
I don't feel that Facebook told anyone that their data would be private. Maybe I'm just naïve, or a little bit of an exhibitionist.