What’s a good response to “It’s fine, I’ve got nothing to hide online”?

David Piper:

Whenever I try to explain my concerns about online data privacy to other people (family and friends, mostly), the most common response I get is:
“Oh it’s fine, Facebook/Google/etc can collect whatever they want, I don’t have anything to hide.”

I try to explain that the kind of data collection (and use/sale) we see from these businesses can be a much bigger concern than just “Facebook knows where I work”, but I can never really articulate my thoughts well.