I've stopped ranking and pushing for YAHOO and MSN a long time ago. but now, there are new search engines on the block like lexxe swicki rollyo etc... i created a matrix at: http://znitchit.blogspot.com/2006/11/ultimate-search-20-showdown.html it might be important to start SEO for these new search 2.0 sites now
Important? Yeah, I guess they could send like... 2 visitors a month to your site? The top 3 are not going to just stand there and loose market
while i emotionally tend to agree with you, Yahoo, MSN and Altavista DID loose the market to a small new guy 5 years ago called GOOGLE.
My swicki at my replica watch site generates about 500-700 searches a day, and about $5 or so currently in adsense revenue with me doing literally nothing. Not only that but the swicki is ranking well for my keywords, which basically doubles my coverage in some SERPs. Pretty cool for something free.