Right, but it's worth pointing out that business models reliant on browser-requested ads are based on a faulty assumption that site owners control clients. Does Facebook's TOS include a statement to the effect of "the user must make a best effort to download all resources linked from each page"?
It's more like I want to go to the store, so I invite the store to send me a driver who will use my car to drive me to the store. The store accepts my invitation, but when the driver shows up he wants to invite a bunch of hitchhikers into my car but I politely decline. Meanwhile, I'm driven to the store.
Your bus analogy assumes that Facebook owns and operates my browser. That is incorrect.
These analogies are stupid, but in your example it's more like you invite the store to send a driver and they say "sure, he's going to bring five people with him", you say "OK, fine", then when he arrives you forcibly eject the five people you agreed to ride with.
But like I said. Analogies get really dumb when you get too deeply into them.