I have to agree with @joanaltres - if we use banners, then the site has to be easily accessible. Think about it - would you pay money to read Facebook articles? :)

So after banners are introduced, I suppose we will be urged to remove any ad blockers and possibly click on a couple of banners every day, so the price of Steem holds. Which brings about another issue - Steemit will steer away from decentralization, as its survival will depend on the whim of the bank account holders, where the advertising income will be depostited.