Why does Google AdSense show public service ads?

Ok, so its only been a week so far and I've already had some experience with the way adsense works. Oh, and did I mention, I've discovered several AdSense NO-NOs. Oh and I also figured out when and why google displays public service ads. I figured that Google will usually display public service ads in one of the following scenarios:

1. Your publisher ID is wrong or improper. Or perhaps you did not comply to the google TOS.
   
2. You tried to modify the adsense code and accidently screw it up.
3. Google can't find any ads to match the content in the page.
4. You did not put the code in the template, and put it in a post instead - The thing that you should keep in mind is always have the adsense in your TEMPLATE ONLY. Don't try and put any adsense code into your posts, because it will not work. Instead you'll just get a ugly ad like the one shown below. Why? because once you post the code through most CMS systems the code will not stay in different lines (the linebrakes between the code will be removed), therefore it wont work.
5. Google might have "flagged" your page? (see below for more stuff on why I think that might be the case)
   
6. There was a hardware malfunction that occured at Google HQ.

Recently, I also had a problem on this page, where google kept showing public service ads. I'm not sure if Google has some approving system where someone has to come and approve a "flagged page" or if it was a hardware malfunction that caused public service ads to be displayed, but I'm sure it was one or the other. I'm certain that there were at least some ads that matched with the content. They page appears fine now though. This is how the page used to look before when the public service ads were displayed and had some intentional mistakes in it(I'm sure you'd agree it looked ugly with all that empty space) :

I've also pointed out some "imperfections" in the page when it was published for the first time (of course, they have been corrected now.. I think..). Perhaps that was what caused the page to be "flagged". I'm not sure. I'll be performing a couple of other tests to find out what the cause for public service ads might be.