There's a notion that companies named after their open source project are more likely to succeed commercially than those that are not. So from that perspective, good for MongoDB. Of course I can come up with a number of counter examples....
E.G. RIM is now BlackBerry Ltd. There are a many reasons why this is the case, but chief among them is that usually the product outpaces the clout of the company/organization (for better or for worse). When that happens, it does make some sense to adopt the product name.