Woodward and Bernstein knew the identity of Deep throat. they were the ones who finally confirmed that it was Mark Felt.
If google is to protect a blogger from a criminal process, Google will not know the blogger. So how will it know right away whether the blogger is a paedophile, scammer, or an activist fighting for someone's rights.
Some might say that this can be found out by reading through the blog, but that is placing undue burden on Google. This is something that is best decided by the court system whether the person deserves to be anonymous or not and whether the person then deserves prosecution or not.
Newspapers and broadcasters have a forty-year history of fighting criminal investigators who issue subpoenas to identify their sources
We should not compare Google bloggers and newspaper sources in this case. A newspaper reporter has met his source multiple times and has made a determination about his trustworthiness and value. Google has never met their blogger and has no idea who the blogger is. The blogger may actually be a criminal or, as in this case he/she may be an anonymous activist. Google has little information to make such value judgments.
So we must not expect that Google will protect their bloggers to the same extent as as newspaper sources. e.g. going to prison for them etc.
"...but the question is what Google does to make sure that access is not just limited, but monitored to avoid serious abuses like this."
Monitoring something in real time is very difficult and is not a productive way to work things. The best way to go is to do a check later on and also at the same time have quick and effective punishment for any transgressions.
This has happened in this case.
I am sure that everybody in Google now knows that their job is on the line for privacy issue violations. It is at least as effective as active monitoring if not more.
looking back right from Napster, Grokster etc there have been free (or very cheap) ways to distribute music. The music industry has, in every case, managed to stop them or mangle them beyond recognition.
The music industry has now set it's sights on p2p (pirate bay). While pirate bay may have won some victories, the music industry will keep on coming with one thing or the other until it shuts it down.
A student of history will also see that this is the pattern for all the other services. They fight for a while, win a few victories but ultimately loose.
The reason the music industry fights so hard is that it feels (rightly or wrongly) that it's survival is at stake. It will keep on fighting until it is able to generate the same amount of revenues through another model or is replaced by another industry altogether.