Just because everything can be run on a blockchain (note: blockchain is just a data structure; a form of arranging data) it does not mean that everything should run on a blockchain.

Many people seem to misunderstand the real purpose of a blockchain. If you just want to add 'blockchain' as a tag for something, you are not making it better in any way.
The problems you are trying to fix can not be fixed by the use of a blockchain.

But.. feel free to outline. How would you fight ad fraud with 'a blockchain' ?