>Didn't the Wangs use the hard sectored disks with the holes so it could find the sectors?
>
>Funny things that pop into the mind ...

There were games distributed on floppies with tiny holes punched in them. Any copying software would skip the affected sectors, but the game relied on the physical layout of the sectors, so the copy wouldn't run. Or a bunch of sectors were artificially marked as bad but the crucial pieces of code were in them.