Unnecessary mixing is nasty too.
The canonical example is the one Scott Hanselman cites; URLs are NOT case sensitive, but the underlying file system CAN be… which means you end up with things like /filename.txt producing a 404 to the file “Filename.txt” because you copied your website from a Windows box to to a UNIX box.
IMO, Unix webservers should honor the DNS insensitive convention since they’re sitting under it. Mixing it up just makes things worse.
And you know what else is nasty? The de-facto default of all lowercase filenames in UNIX to avoid the constant specter of mismatches based on case. Another symptom of the case sensitivity disease.
That’s a completely different issue, but it’s evil for the very same reason: it causes developers to spend extra time debugging. This can be measured empirically; it isn’t a matter of opinion.
So I’m as likely to type in “Cucumber” instead of “HtmlTag” vs. “HTMLTag”? This is news to me…