EPTOften I feel that I COULD defend an early third base, but I just don't have the units to destroy the rocks - it takes a small handful of zerglings a LONG time to destroy the rocks due to the armour (3 armour = 60% damage reduction). By the time a Protoss or Terran wishes to take his third they will already have a decent number of units available to do so, not to mention that many of those units also have bonus damage to armoured and have higher damage attacks (a zealot, for example, only has a 38% damage reduction assuming no upgrades).
The only reason I can see for expansion rocks is to hinder the potential economy gain of a Zerg player. The real question is - is that necessary hindrance?
