Whether they are a big name or not doesn't matter now, as obviously it is Google's intentions to have their hands on the social networking market in a bigger way. Google's exact reasons for acquiring the company are a bit vague, but it's possible they may seek to incorporate Jaiku's services into their existing lineup like mobile searching:
”Activity streams and mobile presence are important areas where we believe Google can add a lot of value for users. Jaiku's technology and talented team are a great addition to Google's current application and mobile teams.”
Neither Google nor Jaiku are mentioning the financial cost behind the acquisition, but as we've seen the past two years Google is not shy about throwing their money around.