I try to go barefoot as often as I can, and my bigger concern in crowds is getting my feet stepped on.

Paradoxically, I am very paranoid about injuring my toes - so walking around doesn't concern me (at worst, I'll step on something pointy and will need a bandaid), but losing another toenail because someone kicks me with a hard shoe is something I dread.

Also: I would absolutely never, ever go barefoot in a big city, which is defined by being big enough to have a train. Stepping on a sharp rock or thorn is one thing; stepping on someone's broken beer bottle and then hiking through all the wonderful fluids that cities accumulate sounds like a nightmare and a free trip to the hospital to get pumped full of every antibiotic known to humanity.