As you pointed out, Google already competes both directly and indirectly with myspace; NewsCorp knew that going in, and went with Google anyway. I doubt that serving ads for yet another social network would be enough to drive NewsCorp away--and I even more seriously doubt that their contract with Google would allow it.
One point about Orkut: while its growth is phenomenal, most of that growth is in non-US markets, so it does not pose any direct threat to either Friendster or myspace.
One point about Orkut: while its growth is phenomenal, most of that growth is in non-US markets, so it does not pose any direct threat to either Friendster or myspace.