With Google, I can see their ability to become a shady company pretty easily, but it is just too damn easy to switch search engines. Bing isn't so bad you know.
But Facebook knows so much about me, and the network effects are so strong -- this is the company I feel most unpleasantly stuck to. Not "Comcast stuck" mind you, but still, more "stuck" than I'd like. It's like my friends keep having parties at a bar I'm not super fond of... and I keep going.