Sadly you are right about that. Omar at ITM ripped into Sadr today big time.
There were no car-bombs, huge explosions or clashes yet more than 80 bodies were found scattered in various districts of the capital and the number is increasing while I'm typing these words.
The most disturbing finding is that some of the victims were strangled and others were found hanging from lampposts with the word 'traitor' written on the bodies and this makes one think the 4 victims in this particular case were from Sadr city itself because 'traitor' is used to describe someone from your own but who turned against you and it makes no sense to use it on strangers.
I'm afraid I have to think that some sort of 'court' is behind these executions because strangling or death by hanging is not the common execution method for al-Qaeda or regular criminals and I'm afraid we are standing before the doings of a new sharia court similar to the one found in Najaf back in 2004 (and we never heard of the results of the alleged investigation ever since).
You form a multi-thousand men militia, you arm them with all kinds of weapons you can find, you fill them with hatred through your inflammatory speeches, you promise to use your militia to defend Iraq's worst enemies, you accuse the Sunni of being Takfiri terrorists, accuse the US of supporting this terrorism and accuse Kurds and fellow Shia of being materialistic opportunists and puppets of the US occupier. And your Islamic militia attacks dozens of mosques and kills dozens of people over night. And after all this you call yourself a patriot.
You are just as dangerous to Iraq as Saddam was or al-Qaeda is. I worked in Basra for a whole year, and I was the only secular person in town of 50,000 devout Shia. They didn't hate me, they didn't hurt me and I never felt afraid of being there. On the contrary, there was a great deal of mutual respect between me and the locals I was in contact with. Al-Qaeda was already murdering Iraqis back then but Iraqis knew who the bad guys were and they didn't alienate or generalize the term 'terrorist' over an entire portion of the community.
It's you and hateful thugs like you who got us to this point… God damn you.
http://iraqthemodel.blogspot.com/"It's only a matter of time before they successfully pull off something like this." - oolatec 
Nope. For one thing, Al Qaeda reveals that they are so powerless now in Iraq that they have to depend upon Iraq's government to make mistakes to enable some attack like this (e.g. Iraqi bureaucrats signing off on paperwork)...and even then it didn't happen.
For another, Al Qaeda's best personnel have probably already been transfered to other areas such as Gaza, Lebanon, Afghanistan, Lebanon, etc...simply because U.S. casualties have fallen by 60% since the October Iraqi referendum. A declining U.S. casualty rate is a sign of Al Qaeda weakness, after all (Al Qaeda could just move en masse to Somalia if they only wanted to destabilize a government rather than shoot at Americans).
So this sort of thing isn't going to happen in the future. Al Qaeda grows weaker every day, per the casualty stats.
This was their "Big Bang" in Iraq...and it fizzled.