OpenSocial offers a way for other social networking sites to implement an API -- e.g. play catch-up with Facebook. Yet playing catch-up isn't the way to beat your competition. These other sites need to find a way to use own unique strengths to differentiate themselves from Facebook (and each other).
Really, the biggest thing OpenSocial has going for it is Google's support and the integration between OpenSocial and the Google "platform". Third-party apps that take advantage of GMail would definitely be awesome. But that's because that plays to Google's unique strengths, rather playing catch-up to Facebook's. Doing the latter would be like Facebook trying to do e-mail and search.
Really, the biggest thing OpenSocial has going for it is Google's support and the integration between OpenSocial and the Google "platform". Third-party apps that take advantage of GMail would definitely be awesome. But that's because that plays to Google's unique strengths, rather playing catch-up to Facebook's. Doing the latter would be like Facebook trying to do e-mail and search.