How would you define being left alone? It is currently based on a very specific mixture of laws and customs that foster private property and other such concepts. You're also dependent on the safety and/or infrastructure in your local area. The wealth that makes this all possible in a developed country isn't attained by leaving people alone, either. I would contend that the idea of being conceptually separated from the community in a Randian sense IS the childlike fairytale in a way.
Besides, there is a perfectly libertarian or even ancap way of looking at the advertisement problem. Billboards affect the quality of a city, and most of the people it affects aren't getting paid proceeds. So they can gang up together to ask for a better deal. And if they can't then they are being restricted by some non-libertarian force.