I agree with ciphergoth's guess.

Eliezer: I agree with ciphergoth and Yvain. Debating, at least as the Theist Who (Apparently) Must Not Be Named is concerned, is a performance art more than it is a form of intellectual inquiry, and unless you've done a lot of it you run the severe risk of getting eaten by someone who has, especially if you decide to handicap yourself. If you engage in such a debate, the chances are that at least some people will watch or hear it, or merely learn of the result, and change their opinions as a result. (Probably few will change so far as to convert or deconvert: maybe none. Many will find that their views become more or less entrenched.)

What would you think of a musician who decided to give a public performance without so much as looking at the piece she was going to play? Would you not be inclined to say: "It's all very well to test yourself, but please do it in private"?

(For what it's worth, I think it's rather unlikely that TTWMNBN will agree to a Bloggingheads-style debate. He would want it to be public. And he might decide that Eliezer isn't high-enough-profile to be worth debating. Remember: for him, among other things, this is propaganda.)

[EDITED a few minutes after posting to remove the explicit mention of the theist's name]