Another proud So Cal flip flop wearer here. I think at last count I had 10 pair. I don't own any of the cheapie Old Navy ones though. They cause blisters between my toes! Reefs are the best!
Almost all of this can be said about heels, too, and I'm sure Cosmo has no problem with them. They can shorten your achilles tendon, they can change your posture, they make you more clumsy, etc.
I can almost promise that on the next page there is an article about "10 fun summer must-have shoes!" and 5 of them are flip-flops.