It was built in-house at Google, not aquired. Orkut (the person) had been working at Google for several years before he built orkut.com. He'd done a similar site at Stanford pre-Google (and pre-Friendster!)
IIRC it was a 20% time project. Up to you to decide if that makes 20% time more or less of a good idea.
Today I learned! The aspx and the lack of branding really had me fooled. And when the Google branding came along, that’s when it started to go down in my circle, so I never knew that it was a Google (20%) project!