Apple are now one of a growing list (including geocaching, and foursquare) to Switch2OSM."
Link to Original Source
So going back to your anology of leaving a car unlocked (with the keys in too?) would you get any sympathy from the Police or insurance company? Oh no, you'd be laughed out of the building and charged far more on next years premium. Sorry, thats wrong - you'd lie and make a claim increasing everyone elses premium.
- By leveraging their position in people's minds, and the popularity of their other products
- By crosslinking with other products - direct integration with gmail, for example, or including a module to google-index local files.
- By producing a damn good product (something they do have experience of)
That's off the top of my head. It's the usual way people compete, after all.
PS: Opera isn't open source, btw