Liberals have not had a comparable public philosophy debate. A year ago I called the head of a prominent liberal think tank to ask him who his favorite philosopher was. If I'd asked about health care, he could have given me four hours of brilliant conversation, but on this subject he stumbled and said he'd call me back. He never did.
What a strange question. I certainly can't name my favorite philosopher. And it's not just because I'm not an expert in the field. I can't name my favorite cryptographer either.

I'm deeply hurt.
Well, obviously you're *one* of my favorites, Dan... Maybe if you came to the gym with me you could win the coveted #1 spot.
Well, Dan, you might have been a favorite until that cheeky comment about the ineffectiveness of us intellectuals, but now I have to give the nod to Bruce Schneier. :P
(I'm kidding, actually. I'm more familiar with his work than yours, but I actually agree with you about intellectuals, much to my own chagrin.)
The utter irrelevancy of contemplating the works of philosophers to thoughtfulness in general aside, there is something of a point in that not only could the "head of a prominent liberal think tank" not expound on philosophy, but he couldn't even come up with a pithy quote or even a name for deflection. Bush obviously is not big on following the philosophies of Jesus, but scored major points by being able to drop that name on command. I'd kind of expect the head of a think tank to be able to come up with something at least vaguely defensible in a short period of time. He can always change his mind later.
Philosopher: probably Popper, though there are others high on my list.
Cryptographer: I'd say, but I know too many and don't want to insult anyone by naming someone else.
Neat. I was leaning toward Popper, too. OTOH, Bertrand Russell has a pretty good vitae. Brooks' opprobrium notwithstanding, it is kind of a silly thing to ask. Even on those "desert island" questions, they generally let you pick more than one book or recording or whatever to bring along, after all.
Given Brooks' polemical point, now that I think about it, I'd have said J.S. Mill, but that would have been more to "come up with a name for deflection".
As for cryptographers, I haven't the foggiest.
All cypherpunks should give homage to the patron saint of anonymity technologies, David Chaum. He's said to be hard to work with, and it's unfortunate that he's publishing more in the patent office than the journals these days, but you can't fault his brilliance. His key patents are beginning to expire and his technology is still amazingly versatile and full of potential.
Adi Shamir!