Cranks take up less room at my shop when they are on end, and yes, occasionally they get hit and fall over like domino's!
A wise sailor once said: "You rolls your dice, you takes your chances"...LOL
That is where I am at too.
I would lay them down so they don't get knocked over but I just don't have the room.
On Crankshafts that have crank sensor tone rings that can be easily damaged, I bolt them to a flywheel to prevent them from falling over.
Any automotive crank that would flex enough to be damaged when laying or standing would be worthless in an engine anyway.
