Context is everything. If you saw a youngster wearing them you'd think they were having a laugh.
If the vicar was wearing a pair when he called you might raise an eyebrow.
They are apparently very good for running and climbing.
We weren't born with shoes on and our feet are not designed to have shoes covering them so the idea is to allow a more natural movement of the foot and to let people return to a more natural running style which is better for the feet and legs and reduces the risk of injury.
I can fully understand the idea, not sure I'd wear a pair to the shops though!
Sallybb, I would imagine they would be an asset if you suffered that way, keeping the toes separated would surely keep them cooler, toes all bunched up in sweaty socks are the haven, surely!