How many adsense ads do you put on your sites? Is the max (3) overkill / offputting? Do you find having more changed the ammount of click throughs? Or did it deter them?
I usually put one in the header, one in the main and one in the footer. Unless the site is fairly small and doesn't require scrolling. If that's the case, I only put one or two.
I put a unit near the top, a unit below the fold, and one elsewhere...footer, side, deeper in the body, whatever. I try not to have more than one in view at a time to avoid the spammy look.
Google officially allowed only 3 Ads per page wither text or image, but you can use small text ads as many as you can with search toolbar.