Should MS buy LinkedIn?

How come none of the big companies have bought LinkedIn? Is there a reason?

And if that were to ever happen, wouldn't MS actually be a great fit?

And wouldn't MS be crazy to let someone else have them?

MS probably couldn't make headway, even if they tried, trying to compete with the likes of Facebook and Twitter. I don't think they want to try. And they probably couldn't buy them. Though maybe they could, who knows?

As I see it, LinkedIn is very work/professional focused, which MS is. It's a popular, useful social network, which MS should be interested in. But it stands apart from the big ones because of its focus. Microsoft could integrate a lot of it's services and since a lot of them probably use Windows at work, if not home, Skype or Lync, and Office, it would be a good fit.

Right now LinkedIn's annual revenue is short of a billion dollars. I don't know what they should cost to acquire though.

It just makes sense in my head, so I wondered why they wouldn't make a big play for them the way they did with Skype.