I hate flip flops. I have this irrational fear of wearing them and then being chased by something dangerous and not being able to run fast enough.
My gym isn't very busy, and no one ever uses the showers (yet they're cleaned quite often). When I joined a few months ago I'd just stay barefoot.
One day I stepped in the shower only to find something white on the floor (you fill in the blanks).
I don't shower at the gym anymore, but if I did I'd NOT be going barefoot.