Oooh, I was waiting for that phrase to come up. Many feel that the text to html ratio or text to code ratio is not a factor. I think otherwise. Also, once you come up with that percentage, then you need to determine what percentage of that is duplicate. Subtract that and you are left with the percentage of unique content, that is what counts. Minimizing the impact that a Mega Menu would have in this instance is of great concern for many.
Ever see the commercial with the State Troopers aiming their radar gun at a car dragging an anchor? Its funny! They start giggling when the radar registers 12 MPH and then an oil sludge promotion comes into play.
That's how I view websites with large navigation structures. Many times they become anchors in the true sense of the word. Most sites cannot handle the type of internal link architecture they are being bulked up with. It dilutes "everything". You cannot logically focus a website when the navigation structure remains "un-focused".
Now, the Wiki, what a piece of art that is. That is pure genius from my perspective. Google seems to agree too. Oh, and so do the other SEs, the few that are left. At some point, you become so large that navigation is no longer a factor, you rely on search and other on page methods to navigate through an array of taxonomy that is specific to your "experience". Its a rather "divine" concept if you ask me. :)