Facebook, MySpace Making Joint Announcement Thursday

MySpace (NSDQ: NWS) and Facebook plan to make a joint announcement Thursday on an unspecified venture, according to an invitation issued by MySpace late Wednesday.

All the e-mailed invite specifies is that there will be a webinar noon PT on Thursday, to be hosted by MySpace CEO Mike Jones and Dan Rose, vice president of marketing and partnerships at Facebook.

Given that the two companies were arch rivals just a few short years ago, the collaboration is a shocker. However, MySpace did effectively signal it was out of the competition last month after it repositioned itself as a social-entertainment destination. The change was intended to stabilize the News Corp.-owned company after years of struggle that saw its dominance of the social networking space effectively up-ended by Facebook and Twitter.

While ceaseless rumors suggesting News Corp. would like to sell MySpace could kick up a fresh round of rumors–who else but Facebook could absorb the still sizable footprint of MySpace–the presence of Rose for the announcement, as opposed to say, Mark Zuckerberg, makes that quite unlikely. Plus News Corp. president Chase Carey indicated during News Corp. recent earnings call that it would be patient with its acquisition–at least for a few more quarters.

More likely theory: British newspaper The Telegraph reported earlier this week that MySpace intended to import Facebook Connect. While certainly a sign of just how huge a shift MySpace is making from its former core competency, the site’s most recent redesign already attempted to integrate external social functionality such as Twitter.

Check back tomorrow to find out why Facebook friended MySpace.