Nice thread. I was also thinking of creating a thread about SEO's quantitativeness.
First I would like to state that my likening of SEO tasks to Feng Shui, is based loosely on a newbies perception of both SEO and Feng Shui. I really would not want to brand feng shui as snakeoil or SEO for that matter.
The thing is, I am a developer by trade and training. I have this attitude of quantifying (or at least try to) everything I see. I even rank women by a deck of cards (3 of clubs the lowest and 2 of Diamonds the highest).
The closest part where I think SEO and FS closely resembles each other, is the way they have been treated, and the way they SHOULD be treated. Most houses apply FS when the house is in the finishing touches. This wreaks havoc on the builders and sometimes even being forced to literally transfer the main entrance. SEO, in some cases has been treated the same. Sites are made up to 80% and then an executive decision is made to make the site SEO compliant. I guess you see this point.
Another point, is that I wish both SEO and FS are applied DURING the planning phase.
SEO is closer to a science than FS, that is true. But SEO cannot accurately predict the number of clicks per day that a site will get in the same way that FS cannot predict the volume of good luck that will come in.
This is where FS and SEO departs from each other, AND where I wish SEO becomes more quantifiable. FS brings in luck, totally unquantifiable. SEO brings in clicks, views and dollars.. something I believe is VERY quantifiable. Or at least have a scoring rubric of how SEO compliant a site is. The problem that I see here is that a common measurement (for all SEs) is not available... yet.
What I wish for SEO (and I will help achieve this) is to have a numeric, quantifiable figure that I can give, when a client asks me "How is this going to affect my site?"
oh.. and
here is another thing that I believe is taken for granted but proves costly...