Luckyfucky - flip flops aren't like barefoot walking, in the same way that ballet flats aren't either. When you're properly barefoot, or in shoes like Fivefingers, you naturally land on the forefoot and roll off the toe.
But in flip flops or ballet flats, people tend to heel strike and kind of slap their feet down. There's also a tendency to overpronate - you see this a lot in ballet flats especially. And in flip flops, people screw their ties up to keep them on, leading to the "waddle."
I'm a fan of "barefoot" running, which is why I've read up on this stuff, and now I really notice it - especially when people are wearing v cheap, thin, ballet flats. it stops them walking properly.
Anyway, back to the thread! I'd just add - Birkenstocks or decent sandals are good, thin ballet flats look cheap. If your sandals are falling apart, get new ones - ruined shoes change a whole outfit IMO.
Loud patterns are usually a bit hideous but, if you're going for it anyway, think ahead and plan your outfit.
The number of times I've seen a garish patterned Joules-esque raincoat thrown on over a clashing patterned dress, because the wearer got caught out by sudden rain or wind on a changeable summers day...