It is a mildly risky but potentially brilliant counterstrike against Facebook’s rising popularity.  Myspace will announce shortly that they are joining the Open Social movement spearheaded by Google and which is now officially a social juggernaut of global proportions.    TechCrunch seems to have the latest on this breaking story.

If Facebook was worth 15 billion yesterday I’d suggest it just dropped by more than 50% in value.   Why?   Without Myspace’s hundreds of millions of users Open Social looked like it would be a third player in the field, struggling to catch up with the user bases of Myspace and Facebook and keep up with Facebook development.   But  not any more.  With Myspace, Open Social instantly becomes the key social network, dwarfing Facebook by any reasonable measure of prominence.   Can new Facebook partner Microsoft help sway onliners and developers to stick with Facebook’s “partly open” architecture instead of defecting to what appears to be a very open Google architecture?   No way.