Maybe it was one of my sites I have seen postings about people struggling with Yahoo, if you take the MSN technique and make sure there is a decent amount of on page copy. Around 300 + words. Then put a fair amount of inernal linking in place, using the key phrases and similar words to help focus the landing pages. Then do an article submission per landing page. If you have around 5 pages at the top level then this will work very well. Link internally to the deeper pages with a few links from the top pages. So if you have 5 pages, have 3 or 4 pages with one link on to the deeper pages. Make this link an inline copy link and not part of a <li> or nav section. (this does not mean dont have it in the nav section, naturally the navigation should point deeper to the section headers). If you get a deep page, then you will need more links to help raise its profile, this should be done with prominent internal links and some article or blog external links. I did an experiment with some directories and a blog, I got a blog last week to page 2 of Google for a competetive travel phrase WITHOUT any backlinks. A day later it was nowhere to be seen. I also saw a posting on DP a few days ago where someone had done no SEO at all, in fact they deliberately broke all the on page SEO rules and just piled the site up with backlinks and got great results.(sorry for not giving poster credit, will dig out thread and add) I would say that to optimise just MSN is a waste, MSN will allow very spammy things. If you optimise for Google and just pile it with backlinks, then again I think you are missing the target. The best way I feel is to have good well written content so a user gets benefit, have it well laid out so a search engine gives you the recognition and the user can read it sensibly, have some good quality internal linking again to help the user experience and to help search engines, have some well placed valuable outbound links and have some really good quality in bound links. If you do everything then you should be ok. One of the biggest failings I see, is when someone reads a snippet on a forum and then takes it as read that this is the answer to the meaning of life, msn, google and the universe. Quite often a post in response to a particular point and not the total solution. I do find that many of my posts get taken out of context. Maybe I should do better postings.
PS I find that Yahoo loves links, articles and footer links from existing websites go down well. A footer link on a forum for example is a great one to do. MSN will like them also, just because they are not required does not mean you should not do them
I think some people mis-estimate their MSN traffic because Live.com is not reported in some analytics tools (such as awstats).