A lot of Ads is always distracting to the users and ruins the visitor experience. Apart from this Google Adsense limits the number of Ads per Page to 3 Ad Units and 4 Link Units and if you add more Ad units to your pages it will appear as blank Spaces in the site.
How to show Different Ads to Visitors from Different Countries
You might wish to promote Affiliate products in the US while delivering Adsense to the rest of the World. With our new Geo Targeting mechanism you can control who see which Ads with just a few clicks.