Hardware and performance

That's a long series of deductions based on some questionable assumptions and logic (I did mean browsing users, by the way, not hits).

For example, I would query your statement that more content means more accesses, since it's the dynamic content like forums and quizzes that cause the most hits (not much happens to display static content on the screen, especially long pages of text).

I would not support that 90,000 figure, and I have no idea if a better average number would be higher or lower.

You're right in saying that clustering is a good solution for large institutions (imagine the web traffic sourceforge.net is handling).