"Those shoes have no arch support!"
Yes, the tired refrain of someone wearing tank-like shoes with tons of sculpting for "support" when they see Vibrams or other totally flat thin-soled shoes.
You'd think that from three years of such "unsupportive" shoes that my arches would have damn near collapsed. But quite the opposite has happened: they are taller and stronger than ever. In fact they are so well-developed that my shoe size has decreased quite dramatically. In high school I was a size 7. Last year I was buying size 6, but I thought maybe the brands I was buying were unusual. Much to my dismay, this year I'm more a 5.5 and now I know it's not some sort of weird sizing issue. My feet are not wider though, maybe they would be if I did more unshod barefoot running.
It's very hard to find women's sandals that are totally flat and with a thin shoe. They either seem to be flat, but with an "Earth mama" "supportive" thick heel like these things...
Or they are cute and feminine, but have a cheap standard sole with a small heel:
On a fluke last year I found some great gladiator sandals at Payless, but they literally fell apart recently and the new items at Payless all have hideous heels. So I splurged and got the Flex Collection by Cole Haan Women's Air Vernonia Gladiator Sandal
It has a nice thin flexible Nike Free sole. Unfortunately the straps are quite uncomfortable and I'm still breaking them in a week later. I'll review them eventually, but if you know of a totally flat AND feminine sandal with a flexible sole, post it in the comments.