Well, you see, painting toenails is a way to add beauty to a gross part of your body, sorta like giving the hunchback of Notre Dame a nice haircut. I don't think it's a fad, people have painting their toenails red for some time now.
It's becoming quite popular at certain health 'spas'. Excema (sp?) and psoriasis sufferers travel to places that have huge numbers of these fish and get in the water. The fish nibble off all the dead skin and flakes... Dunno if it's a permanent treatment though... .