The Register: Security bugs floor Google's Friendster-clone
According to the Register, it wasn't scalability that took Orkut offline, but security issues. The article bashes Google on several fronts, including their policy of letting coders experiment with projects on their own time, which helped the genesis of Orkut. The article also mentions that Orkut was developed on a windows platform, and for Google that would be unusual, particularly if they desired the venture to grow within the same infrastructure as the rest of its Google Labs projects.