I think on page factors have little weighting. They are too easy to abuse. Saying that the only on page I do is a title tag, meta tags, and having the keyword repeated several times on a website.
I once saw a pharmacy website ranking #1 for casinos on yahoo. The webmaster must have confused the two websites that he was blog spamming. That kind of gave me a clue that most of the weight is given to inbound links.