Why does almost every banner ad here seem to be a Google /doubleclick add for the life of me, I can't explain it. You hover the mouse over the side banners and almost all say google adservices.. hummn,, interesting....
Looks like an even dozen 250x250 format ads on one page. The limit is three. So, there are 4 times too many ads. This is pushing your luck too far, I think. . .
Perhaps they are premium publishers and can have different rules, but it's more likely that they're using iframes and will get banned or will receive a warning from adsense.
They are not going to get caught doing anything. They are a very high traffic site. Google is working with them. If you are just an ordinary publisher you can not display more ad units than the limit. Try it and you will see the GOOGLE WILL NOT DISPLAY ADDITIONAL ADS ON YOUR SITE EVEN IF YOU PLACE THE CODE.
Google will display unlimited ads if you use iframes. In the case of this site they are using javascript to generate one iframe per ad. but as you said it is a high traffic site and might be premium publishers and have agreed with adsense for the setting they have.
I personally wouldn't want any of my sites to be invaded with ads like that. It's ugly, it's distracting (actually hard to focus on the actual content), and it tells visitors "we are here making money, click the ads or die!!!!". I don't care how many Googles they work with, this is just an easy way to profit more at expense of your site looking more like shit, something that not many people would want to trust. 3 adsense blocks is more than enough to make you well off with the right website layout and great content.