Well, that'd be odd. Then when you're trying to summon him, everyone would camp in the hills and kill you as you are wishing.
That rock idea is a good idea. After a wish is made, they turn to stone and shoot off. Then after 1 or 2 minutes is up, they are DB's again. The balls also DO NOT show up on radar until they are normal DB's again. So this would help prevent people from collecting them before two minutes is up. Also, when they are rock, they will be harder to spot in a mountain side since they blend in. The current balls blend in, and they are bright orange!
O_O
Anyways, good ideas people.