I never really saw much mention of this but Yahoo Suggestions (Search Assist On when you type in at Yahoo.com) was being heavily gamed for about 2-3 weeks last month. It looks like they've since cleaned [some] of it up.
Big money keywords that were appearing in the suggestions all had some special code at the end of them such as tip2008, d3, z7, etc. So when you'd start to type mortgage refin into Yahoo the suggestion box would pop up with mortgage refinance tip2008 as the first result. Of course when you choose that result someone had created a spam site optimized for mortgage refinance tip2008. They did this for a lot of high dollar terms - mortgage, real estate, online colleges, loans, and on and on.
And while I while I didn't take advantage of the situation by creating any pages optimized for those terms, at work we did start seeing a lot of YSM clicks coming through with those terms for our college keywords (meaning people use the suggestions a lot). The person who did this created a bunch of optimized sites on zoomshare that all redirect to shitty adsense like landing pages.
Actually if you search Yahoo for Mortgage Refinance R you should see the suggestion for one with y8 appended to the term. So it looks like they didn't clean everything up.