Limiting number of domain registrations per-person probably won't work, because one can get thousands of sockpuppet "shareholders", each having registered a sol

Limiting number of domain registrations per-person probably won't work, because one can get thousands of sockpuppet "shareholders", each having registered a sole domain. And parking domains is indistinguishable from using them. Unless under "parking" you mean explicitly stating this domain is for sale. But with imposed restriction squatters will just remove those and park domains with "this domain is... well, you get the idea".