I had a similar idea in college which was to take the actual traffic for pages into account for search ranking (this was before Google bought whatever Analytics had been called before, I can't remember.) I had thought of it as a server side app which would benefit the hosts while feeding the search engine traffic data.
After talking with friends we explored the idea of a user side traffic tracking app as a way to feed the search engine, but I couldn't get enough traction and no one wanted to challenge not only Google but also IE/Firefox/Safari etc. because we felt it would be its own browser.
Now a days I am more concerned about possible privacy issues, I feel for them launching a search engine that actively asks you to be tracked (even if anonymously), it's a hard sell during this current resistance to that entire idea.
At the time FF was still behind IE and IE hadn't really adopted extensions yet, I think. It's a bit fuzzy how we got there, this wasn't like a formal business plan and analysis, this was some college guys in the dorms chewing on an idea for a few weeks.