SEO history based on my experience – a very late at night post.
1999 SEO – Creating 18 doorway pages for 18 major search engines. Looking at the sites in the top results and analyzing keyword density of each area of the pages, and repeating it with just a little more keyword density. Regularly submitting pages to the Search Engines.
2000 SEO – PPC at 1 cent per click at GoTo (later Overture/Yahoo). Yahoo owns 1/3 of the internet, MSN (Looksmart) owns ~15%, and another 15 engines share the rest. Google who?
2001 SEO – 3 major directories control much of the Internet. Yahoo Directory (~35% SE traffic), Looksmart Directory (top of MSN results), DMOZ (Helped in several search engines (including Google)). Being an editor for Zeal (Looksmart non ecommerce Editors – showed at top of MSN) and becoming a DMOZ Editor could control your listing. and with directory editor experience, then submitting to Yahoo with urls like www.car-parts-auto-part-cheap-discount.com. Back then you could have #1 rankings in 1-3 days accross 90% of the internet.
2002 SEO – Refining Keyword density and stuffing in 1 more keyword on your pages than the top guys have. By the end of the year Google’s taken over King, and the other search engines are fading fast, and the days of SEO link building are Priorty #1, trade them and buy them.
2003 SEO – With Yahoo now defaulting search results to Google, Google now controls 79% of all searches. MSN is a far cry #2 with ~13%. With Google ruling, he with the highest PageRank and most backlinks, and focused anchor text links wins monthly rankings in the Monthly Google Dance. By the end of the year almost everyone will feel the effects of a search update gone wrong with an updated called "Florida".
2004 SEO – After Florida update, back to PPC in the Mix, now with a choice of Overture or Google Adwords. Monthly Google dances end, and something called the "sandbox" kicks in (site aging factor in google). Now 3 major engines (Google at ~55%, Yahoo ~35%, and MSN ~6%) with all major engines focusing on links
2005 SEO – Yahoo and MSN, pound with lots of links at once and keep pounding with anything you can get for backlinks with a focused backlink text campaign. With Google, the older the site the better, slow and steady link building with a large variety of backlink text wins (notice it’s the opposite of yahoo and msn).
Future SEO – Backlinks within content of well placed sites within related neighborhoods? Personalization? localization? Content? TrustRank? What else?