Orkut: 500,000 and growing

Orkut’s news page announced yesterday that they moved their servers(that’s why they were down), and that they are about to hit 500,000 members.
According to the member stats, only 35% are from the US; 24% are from Brazil(!)
Given that Orkut launched the end of February, and that the site is invite only, what do you make of this rate of growth? Seems pretty good to moi.