Of all the new brass I've purchased, one piece had a flash hole so off center I doubt the primer could have ignited the powder. I've never found a piece with no flash hole.
For lesser degrees of off centeredness, there wouldn't be any concern safety wise. In some CMP 30/06 ammo I bought, much of the brass has off centered flash holes and yet all goes bang without any problem. That said, I don't see how an off centered flash hole can contributed to good accuracy so I don't reload brass with off centered flash holes.
