That's called a clean room implementation and was the standard way to make x-compatible products (like for example, the bios on an IBM PC clone). Not sure what the current legal standing of that method is.
EDIT: Ninjad because I left the reply in a tab without posting.
This actually seems like a good idea if it just shows up when in your map view rather than pulling your view to the pin. It would be well targeted adds without requiring you to collect data about the user. If its visible it's because you're close.
EDIT: Ninjad because I left the reply in a tab without posting.