How People use more than 3 adsense code at one page?

I saw many website put morethan 3 adsense code at one page.
Google AdSense offers different types of ads, and most are categorized in the following formats:

• 3 AdSense content unit
• 3 AdSense link unit
• 2 AdSense for search

So i think its possible to show total 8 ad unit on page with different ad unit.

But some people are using 5,6,13 Banner ad unit on one page.
For Example:
phonearena[Dot]com Using 13 Banner ad one page
caandesign[Dot]com Using 5 Banner ad one page

How it is possible?why Adsense didn't suspend their account?
Or something wrong with me to understanding ?What is the maximum number of AdSense units I can put on a page??

They are a premium publisher, It's invitation only.

Those ads are not from google adsense only, its from google ad exchange. I used 3 adsense and 3 more ads from sovrn

Hope that help

Viral websites can discuss te number of ads with google !
but the default number is 3 content ads, 3 link ads, 2 ads search

I managed to get 5