Reputable or not.... I always feel like when the internet zigs... Google zags... all in order to keep page-ranking "cheaters" from beating them at their own game of ranking web content using 200 threads/streams of data.... and yet, I STILL can't find what I am looking for half the time and end up in link-farms, and ad-bogs instead of finding useful pages on programming tips/forums....
So, even if the SEO folks are not just Voodo Priests, they will certainly NEVER attain a lasting level of expertise as long as things are not standardized or stabilized.
The companies with more money will always be able to buy more outside links, faster web servers, and better programmers... so does that mean their sites are actually more RELEVANT to the people who are searching for information?
I don't think so.
And that is why I really think SEO is more like a merry-go-round than a con.
It is a self-perpetuating system of reactionary commerce with no hope of ever getting off.