Thought this may interest more than a couple of people here:
The most common question I get asked about Google's ranking is "how do you do it?" Of course, there is a lot that goes into building a state-of-the-art ranking system like ours, and I will delve deeper into the technology behind it in a later post. Today, I would like to briefly share the philosophies behind Google ranking:
1) Best locally relevant results served globally.
2) Keep it simple.
3) No manual intervention.
Read the rest here:
http://googleblog.blogspot.com/2008/07/introduction-to-google-ranking.html