So how exactly are you planning to use the technology for ads in blockchain ? I doubt anyone will volounteer to watch ads on your page ... So how is it different than image hosting on some ftp ? Technology is nothing if u can't use it.
I think you are getting confused with "classified ads" and "ads". If Bob wants to sell his motorcycle and lives in Rome and Bill wants to buy a used motorcycle and lives in or very near Rome - Bob posts the ad on the blockchain and Bill uses the wallet or search engine on the CraigsCoin website for "used motorcycles near Rome for sell."
It not like we have to watch website "ads" from companies trying to entice us to buy stuff we don't need similar to how youtube makes money to host videos for free.