[thagsimmons]

This is too simplistic a critique. One species colonizing everything is perfectly compatible with the model in the broad. The complication is that we ourselves exist, are not colonized, and can look out into space and don't see any alien activity. Hanson starts from this anthropic fact and tries to reason about what we might be expected to see if a) there are "grabby" species out there, and b) we're early enough to witness the land grab. I have problems with the details of the model, but I think it's both a fruitful and interesting attempt to think about things.