Roam-e Prototype Available in 10 Days, page-518

Just FYI - not exactly true.

The forces of air-drag on the rotors (forcing them to be pinned back) is fighting against the centrifugal force wanting them to spread out.

Usually when this happens, the centrifugal wins out and the blade get very close to 90 degrees, thus if you had a small locking mechanism (idk like a small magnet or sprint that helps the thing get to and lock at 90degress) then you could get almost full efficiency out of the blade.

Usually the reason why wings are locked on helicopters is because safety wise it's actually far better to have them locked on a helicopterfor safety.

I'd say RC copters haven't bothered so far because most are really small, flown by professionals or just trying to be cheap.

Not saying IOT design will be perfect, but I did a lot of research into the possibility of this feature and it is actually pretty achievable.