5 out of 7 isn't good enough ? I thought it wasn't good for one pool to have all or most of the hashrate, or is that a lie being spread by smaller pools?
On another note net hash is steadily increasing! In just a few days it's grown from .4 to .7-.9
It's a single point of failure for the coin if everyone is on the same pool, but that's pretty much the only downside. 51% attack is not really relevant for "small" coins, any scrypt pool that has more than 700MH/s (hash.so has 2.5GH/s) could 51% attack CorgiCoin, it doesn't need to be a CorgiCoin pool, obviously other coins are just as vulnerable to it.