I am considering monetising my site a lot more by adding more ads above the fold. I've always held back on the ad front as I've tried to build the site as 'clean' as possible worrying a little that too many ads spoil the site's SEO. I've always run one large ad at the very top of the page which has been necessary and non negotiable for me as the site needs to justify its hosting costs but there are decent sized spaces above the fold on my site which could definitely host new sizable ads. Is my worry justified? No content will get vertically 'pushed down' below the fold as the ads I'm considering will just be put into the free space at the moment on the sides of the content.
I know a lot has been talked over the last year or so about above the fold and below the fold and SEO and I think that definitely merits discussion but my question is more a space utilisation issue I guess. If you have space above the fold and want to monetise it am I likely to experience any negative SEO effects?