I think the reason for the increased risk from wire flooring is due to the wire itself not being completely smooth (some wire flooring can have very, very tiny jagged spots that are easy for small animals to get lacerations from), and people not keeping the wire floor clean (basically thinking that since chinchilla poop falls through they don't need to wash down the wire flooring as often). This leads to lacerations on the feet, and then running through their own pee (which is usually still coated on that wire flooring) which leads to bumblefoot. I think the majority of people who have solid flooring do a better job of cleaning. This is, of course, speculation based on what I have read online. I personally have a spray bottle of white vinegar and water mixed that I will be using at least once per week for my chinchilla cage, as well as spot cleaning any messes they make daily. From all that I have read bumblefoot is bacterial, so keeping the area the chinchillas are in is essential to maintaining good health among the little guys (and gals).