I think the perspective here is a very interesting one. Typically, such transactions are seen as between a user and a service provider. There is an agreed-upon protocol, and so long as everyone sticks to the agreed-upon protocol, the exchange can be successful: this is the basis of Email, the Web, etc.

Taking aside advertisement for a moment, what you're suggesting is that the level of control should go as far as which clients are allowed to speak a given protocol. This would be similar to the landline system during the monopoly days, where you were only allowed to connect an officially-approved phone (with a correspondingly high ongoing rental cost) to the copper lines.

From my perspective, there is no 3rd party involved here: there is an API surface which is developed and supported, and there is a client/customer who is interacting with the service through that API. Advertising either needs to be implemented into the API (good luck--see the demise of RSS), or the 1st party needs another business model.