That's exactly what I do now (but I mixed spellings in my pre-WW-Life). Unfortunately Google keeps old copies of e.g. "index.CFM", "iNdeX.cFm" etc. That means,
1. people get old Google-Caches
2. Google might treat this old Versions as duplicate (multiple) content.
So I want it to drop all the old copies, by putting them into the robots.txt file. As I said, this works just fine with Google.
But I'm not sure how e.g. Altavista would react if it finds "iNdEX.CFM" disallowed. Would it read "index.cfm" anyway or just go away?