First reported by Silicon Alley Insider and then confirmed with additional detail by TechCrunch, Google has added more high-profile partners to its OpenSocial initiative. They are MySpace, Bebo, and SixApart, which now join LinkedIn, Plaxo, and Friendster, among several others, in the alliance or coalition.

The inclusion of MySpace, which has now apparently abandoned its own open platform effort, means that Facebook faces a huge strategic decision about whether to join or “go it alone.” The OpenSocial effort is a response in part to Facebook Platform and its success.

If Facebook fails to join the effort, it risks being seen as isolated. If it does join, some will see the move as a concession to Google and Google will likely be seen to have trumped it — and, by extension, Microsoft.

There’s more discussion at Techmeme.

Postscript Barry: Robert Scoble just posted a quick video interview with Google’s CEO and MySpace’s CEO. Here it is:

Related Topics: Facebook | Google: OpenSocial

About The Author: Greg Sterling is a Contributing Editor at Search Engine Land. He writes a personal blog Screenwerk, about SoLoMo issues and connecting the dots between online and offline. He also posts at Internet2Go, which is focused on the mobile Internet. Follow him @gsterling. See more articles by Greg Sterling