A quote like:
"Data can either be useful or perfectly anonymous but never both."
needs a bit of background about the qualification of the person making that claim. Why? Simply because it sounds like a rather technical remark. If some computer science researcher made this claim, I would tend to take it more on the face value, otherwise I would take it with a grain of salt.
Paul Ohm has degrees in CS and EE. Quoting his rather impressive CV[pdf]:
Yale University, B.S., Computer Science, B.A., Electrical Engineering, 1994
Paul is also a hobbyist Perl hacker. IMHO, this paper is a great example of people in the law community understanding what is going on. We need more people in law who understand tech.