It seems like Microsoft doesn't see much value in having their own data these days (assuming that the point of bing is searching the data rather than the data itself). They canceled Encarta last year, for example. I think it actually makes a lot of sense for them to skip trying to create and maintain the database, which is likely to never be outstanding, and instead focus on writing software to make use of a freely-accessible database that they can contribute a bit to. If you can't have notably better maps than everyone else, you can at least make sure that the best maps are ones you can use, and differentiate your products on something else.
It's not really a new strategy for Microsoft, even; consider how much encouragement they gave to PC clones starting in the 80s, including sharing a lot of information on how the hardware would have to act in order for Microsoft's OSes to run, when IBM might have preferred not to have an open standard. Microsoft wasn't going to get big margins on hardware, so they made sure nobody else would either, letting the competition drive down hardware prices and leaving people's budgets free to spend lots of money on software from Microsoft.