This is a very thorough and useful guide. I've always been pretty turned off by the SEO "community" as guides like this mostly come across as guesswork and quackery.<p>On a personal note I read Andrew's ebook a while ago (which is very good) and had a brief email conversation with him. He struck me as very genuine and knowledgeable guy - even if he was an investment banker! :-)
It's interesting how the nofollow tag has evolved over the years. Originally, people used it not only to control blog SPAM but also to shape the way PageRank flowed throughout a site - a method called PageRank Sculpting. The idea was you'd nofollow links to unimportant pages on your own site so that more PageRank would flow to the important pages you wanted to rank for.<p>I'm pretty sure Google has confirmed this doesn't work anymore. Now a nofollow link still takes a portion of a page's PageRank just without passing it along. Hence, no more sculpting power.
Agree with the others -- solid piece. I get asked about SEO all the time, and I think this is the best explanation while remaining concise I've seen of late. Will definitely recommend this to people before I attempt to explain things.