Forum Moderators: martinibuster
But to answer your first, you can have up to three ad units, plus one link unit, plus a search box, plus referrals. But before you go wild, double check your plans via AdSense Help.
Now, as to your second question, the benefit would be to fill up a page that otherwise had little content. Most people with content find that fewer ads is better because the average click is dragged down by more ads....