Excellent post @jringo. I have one slight clarification I'd like to make:

This makes the pool a major staking entity, which is a form a centralization.

The pools don't stake terribly frequently. Each of the three grcpool accounts have less than 200k GRC (correct me if I'm wrong here). Thus I would not classify the pools as a "major staking entity" at least in terms of Proof of Stake.

The centralization risk is that currently more than a third of all POR rewards go to the pools. This makes the pool a massive target. I also respect BGB and all the great work he does, but the pools having so much control of the POR payouts makes them a very juicy target for would-be attackers.