Realistically, Google will run a monitor. But the important thing to realise is that the monitoring process is completely different from the validation process.

The fundamental idea is to make all certificate creation public, by putting it in a publicly auditable list. THis allows anyone to check that someone else hasn't given out a certificate for their domain, or for a large chunk of the internet etc.

In order to make that work, you have to make all certificates that aren't in that list unusable, and you do that by having the browser check that the certificate it is checking is in the list.