I have a website where in some instances I will know the user's email address. Is there an advertising network, where I would submit an email address to retrieve relevant ads and could then display those ads on the webpage?
Ads based on a user's email address could be more relevant than ads based on the content of the page (and might bring higher ad revenue). Of course, there are privacy concerns, but I'd like to know if this kind of advertising service exists.
Google Adsense knows best. Google takes into consideration not only the content of the current visited website of your users, but also his previous websites and his ads "profile" on google.
Think about it, its one of Google's main sources of revenue + they have access to the users history (each site that displays adsense can track the visiting user, right?) + they have access to the users EVERYTHING online (if the user uses Chrome for browsing).
To sum up, just use Adsense :)