Any activity carries some risk, but we feel going barefoot is no riskier than going barehanded. In fact, unclean bare hands are far more likely to spread bacteria that cause diarrhea and infect people with diseases like the flu because of how much they may touch infected surfaces and our faces. And there are lots of infected surfaces out there, including ATMs.1 Bare feet are unlikely to spread bacteria or viruses because people don't typically touch others' hands or faces with their feet or shoes.

Let's also remember that fungal infections require warm and moist environments to grow. Shoes act like incubators providing the optimal places for this! If people were to go barefoot more often, it would be much harder for feet to sweat and be warm enough to provide the right conditions for this growth.

Regarding other diseases, as long as your soles are clear of open wounds most of these germs will wipe off as you walk. You can also clean your feet as you feel it necessary.

1. "Report: ATMs As Dirty As Public Toilets," TIME, Jan. 13, 2011 (Link)