After getting its final European Commission approvals earlier this week, Microsoft and LinkedIn today announced that Microsoft's $26.2 billion acquisition of LinkedIn, the social networking site, has officially closed. From a report on TechCrunch: The news comes six months after news first broke of the deal. In an internal memo, LinkedIn CEO Jeff Weiner went through the areas where the two companies would be working together, and how they will in other ways remain independent. LinkedIn today has over 400 million registered users, making it the largest social networking site focused on the working world. People use the service both to make work connections with other people in their fields, but also to look for jobs and hire people. As we reported earlier this week, the fact that LinkedIn essentially has a dominant position in this area meant that Microsoft had to make concessions to the EC about how it would work to allow other social networking sites to integrate on its platforms.