Yesterday I wrote on the topic of URL Normalization: Is a Trailing Slash the Same Page, discussing how search engines normalize a URL and what are the SEO implications.
Today I found an interesting real life case of the issues with URL normalization with our friendly search engine Yahoo. The Yahoo Festive Bowties search brings up www.smarttuxedo.com/Festive-Bowties-15 with no trailing slash. I can tell you, that my developers have verified that all links internally use the trailing slash for those pages. So all traffic to those pages from Yahoo went to a 404 page. We will fix that on our side, that it maps to the correct page, not a big deal for us to do.
So you see, Yahoo normalized the URL and stripped off the trailing slash. This had a major impact, not on rankings, but on click throughs going to a 404 page. That reminds me, I should make a custom 404 for smart tuxedo.
I am pretty sure this was not an issue Monday. I remember conducting searches and matching up this with some of my client's sites. This issue was non existent. So this Yahoo issue seems to have recently cropped up, possibly sometime today. I have not seen any other reports of this at the forums as of yet.