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.

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. That memo is copied below.

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.

The fact that these concessions had to be made speaks a little to what Microsoft’s intentions might be with LinkedIn. It seems like one key area for Microsoft will be to upsell those using LinkedIn to recruit, to then buy into Microsoft’s software in areas like HR and sales to extend that functionality.

Microsoft has up to now not really been a significant player in open-ended social networking, although with products like Yammer and Skype it’s clearly put a lot of investment into the kinds of collaboration products that are in demand from enterprises and business users today. It will be interesting to see how and if it tries to marry these two sides of enterprise-focused social networking down the line.

More to come. Refresh for updates.