Just trigger in my mind when I was going through some websites were they having upper case and lower case combination in url something like http://www.domain.com/Home/
I'm going to have to disagree with all established wisdom on this, so I'll probably get downvoted, but:
If you redirect all mixed case urls to your properly cased url, it solves all the problems mentioned. Therefore it seems this argument is coming from tradition and preference. The point of a URL is to have a user-friendly representation of a page, and if your url is friendlier with upper case, why not use it? Compare:
moviesforyoutowatch.com/batman-vii-the-dark-knight-whatevers MoviesForYouToWatch.com/Batman-VII-The-Dark-Knight-Whatevers
I find the mixed case version superior for the purpose. If there's a technical reason that can't be solved with a lower-case compare and redirect, please share it.