The story goes something like (a) people (yahoo) want mobile apps (b) the kid got investors to give him cash (c) people downloaded it generating 'buzz' (d) more investors and cash (e) more downloads and publicity (f) yahoo plays right into the hands of the investors and the hype around a young founder (g) yahoo buys the company, making the kid a millionaire, it's a PR grand slam, bringing more publicity and 'users' to the app (for now)

It works out really, really well for the investors and founder; in my opinion it seems like Yahoo got duped.