How much of the internet is porn?

I read in CNN today that 1% of the internet is comprised of pornography.

This seems like a extremely conservative estimate. The Straight Dope reported a year ago that 83% of the net is smut.

Why such a huge difference in the estimates? I'm guessing that it has to do with how you count the pages (is the number of sites on the internet determined by the number of sites Google has indexed?).

Either way, selling and distributing pornography is a more than $9 billion a year industry in America alone. This happens to be the same dollar amount that would buy all of Africa clean water and plumbing. Nice to see where humanity's priorities are.