That is not accurate. You can have more average ad impressions per day by putting 15 ads on each page instead of 2, but with the same number of users, the performance of more impressions just gets worse with more ads.
I work in advertising and haven't found that true at all. Obviously there's a limit to how many adverts you van usefully place on a page, but clicks tend to relate much closer to page impressions than uniques. What is important about uniques is that each advert should ideally be frequency cap so nobody sees it too many times to get the best results - therefore unique numbers do impact how many impressions you can show of any one advert.
