dogbook vs dogster

Should/Can a media company launch a social network by not launching a social network and just leverage facebook and all of the other social nets that are about to open? Learned in a meeting today that Dogbook, a facebook app is larger than Dogster right now after only three or four months. The app gives you a sub-profile that could serve ads and you could probably replicate this over and over so why bother launching a stand alone? Or perhaps do both?