Ads in the blockchain has been developed by CraigsCoin. Why don't you add it to the BlockNet?
Maybe. I don't know...
That doesn't sound like a good idea though. A blockchain is not the sort of thing to store content. Imagine the bloat!
Content should be indexed in the blockchain and stored, encrypted, on the local storage accessible to multiple nodes in such a way that not even the nodes know what they're storing.