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No other ads are being used so nothing else would be displayed there anyway. Therefore are the few clicks it would generate for probably low paying ads worth it? Or does the lowered CTR have any negative implications?
My best bet would be to tag as much as possible and not leave even a single page untagged and within the scope of the Google policies and rules.
Who knows that one page which you are excluding could get you 15 additional clicks per day. :)
Personally I want a user to arrive at my site and find something useful then leave. Not arrive then click on an advert before they get to know my site.
I realise that this is probably reducing my income from Adsense, but I personally think if a user finds something useful before they leave then they are more likely to come back.
Financially, and from their own branding perspective, google would probably love to have their code on your index pages, and short term it looks good financially for you too as often the index pages are the most popular. But as marketing guy says, you get less chance to brand your own site, which means longer term repeat visits.
Already we are seeing public service ads starting to appear on pages which have mainly external links for example. I know there are other theories and possible causes of the delivery of public service ads, but for us it seems related to the amount of actual content (rather than links) on the page.