While this is specific to flip flops, I would expect that all shoes, esp. open shoes would have very similar results in the types and amount of bacteria picked up. It's more a question of skin contact with that bacteria that creates the problems.
Kinda puts a damper on things for those with a shoe fetish, I'll bet! Best carry a bottle of sanitizer before sticking your faces in them! lol 😉
This is why people here in Japan are absolutely blown away by the knowledge that many people in foreign countries use the same footwear in public, in the workplace, in the doctor's office, and at home. They've known for a long, long time -- culturally if not consciously -- that when one person steps in something dirty, it takes very little time before everyone nearby has been exposed to it.
C'mon, germs are nothing new. They're everywhere and always have been. I mean, you've worn the things for years and haven't developed gangrene or anything fatal, right? It's just more fuel to add to the germaphobia fire.