Well I recently started making a network of literature sites. Each site would feature a different book and well my first yahoo listing finally came through. The site that got listed isn't by far the most popular site. But that single yahoo listing has generated 200 impressions a day, and this isn't even a very well known book.
So if you have a site getting listed on yahoo is a must.
I've suspected that it was highly important. How'd ya like that? The most important search engine to get into, and they're stingy, inefficient and inconsistent in their submission reviews. <sigh>
Aol may serve more overall pages than Yahoo but that doesn't mean that all the pages are portal pages or search pages, not everyone viewing a aol page is looking for something, and the same goes for Yahoo too but the proportion is much different I would think.
In any case I'm in the results for all 3 of them and still Yahoo dominates my referrals.
For the record.. I wasn't talking about MSN in particular but Microsoft in general. Add it up you will see that Microsoft gets almost as many hits as AOL and more than Yahoo!. Though with Yahoo!'s recent purchase of eGroups they may again pull into second place.