R2 for Negative Binomial calculated with GLMMADMB

I have a "meta-theorem" that the only quantity actually calculated according
to the formulas given in introductory texts is the sample mean.

R> x <- c(1e-20, 1, -1)
R> (x[1] + x[2] + x[3])/3
[1] 0
R> (x[3] + x[2] + x[1])/3
[1] 3.333333e-21
R> mean(x)
[1] 0

Looks like he's right!

Kevin