I totally left mountain biking out of my list of categories. I'll need to redo the list with touring and mountain biking to create a comprehensive list of 80 categories.
With regard to mountain biking, if you really want to do mountain biking (beyond the standard fare non-technical singletrack) then that's probably another place where a CX bike would be a bad choice. But I suspect that most people, especially those wondering if a CX bike might work for them, aren't ever (ever) really going to do much more than non-technical singletrack.