I've owned a Fuji X100 and now a X100s. I shoot street and usually shoot very close to my subjects , So F8 (sunny), Shutter at 500, ISO Auto (6400), manual focus at 7 feet and I am ready for some street photography. So out I go to the streets and I see an interesting subject, whip out my x100s , frame > shoot (sometimes from the hip) in a matter of seconds ! Sometime later, I retire to a nice cafe, order a ice mocha ... and settle down to browse thru my shots. Arrrrggh !!! Fully half of my shots are not in focus. Only now I've noticed that my manual focus distance has shifted from 7 feet to 15feet instead !!!
So the issue here to me is, the manual focus ring is so damn smooth that it is very easy for me to unintentionally touch it and shift focus distances. It is very irritating when you are zone focused and need too check the evf/lcd every now and then to make sure your distance scale is correct.
So I brainstormed a bit and came out with a small (maybe inelegant) solution. I dug out an old inner tube for my mountain bike, cut out a strip that is about the width of the focus rings and wrapped over it. The little bit of friction from the rubber prevents the focusing ring from moving from the lightest of touches but it does not affect anything else and I still can adjust aperture/manual focus (turning the ring or AEL/AFL method) as per normal.
I've attached a pic here ...