Those webmasters that stick to old ways and focus entirely on Google are missing out on a lot of search traffic these days if they are not also well ranked by Yahoo and MSN.
For first few months after Yahoo decided to go their own way with natural search (and MSN decided to get serious about search business), search results provided by those two could only be described as bizarre. Enough time has now passed that dust has somewhat settled and there are three main (from a traffic standpoint) sites for quality natural searches.
The term "natural search" is to distinguish true searches, as opposed to paid advertisements which appear in search results for many search engines these days. I guess you can't really fault search engine companies from wanting to make some money (actually, BIG money) selling ad space, but debate over virtues of natural search versus paid advertising search is something that could make up a very thick book and still have no clear resolution...much like debates revolving around religion or politics.
Like most people that have been working as online home business entrepreneurs for a few years, I was strongly conditioned to need to "feed 800 pound gorilla" of search engine world. Basically, "if Google didn't love you", it was very difficult to get any meaningful natural search traffic to your website. Since Google was actually search engine that was serving up results for most of popular search portals, if Google didn't look kindly upon your site and rank you well, you would not be ranked well for most of high traffic search sites on Internet.