The blame should not rest at Pagerank's feet. The moment the web became a place to make money SEO would have cropped up to target any other ranking system, had that become the defacto standard. In fact the ranking system was not raw Pagerank's, it was one of the many signals used to rank a page. It was the resulting ranking that SEO targets, not Pagerank specifically.

i don't think that's correct. SEO has been popular long before google. many websites were overloaded with long lists of unrelated keywords at the bottom.

google became the most popular search engine exactly because those SEO keyword spam lists didn't work anymore and, after a while, they vanished. blogs, on the other hand, worked exceptionally well, because they used to link to other blogs' entries a lot, and blogs also used to be (comparably) high quality content.

so the main SEO guideline for getting a good page rank used to be: have a blog/news and publish lots of high quality content that bloggers link to.

True