I don't know about spending $8.5 billion dollars, but I can see why they did this. They have a good solid enterprise solution gaining traction with Lync. They have a cool videophone thing with Kinect. Downside: limitations on who you can talk to outside the firewall and the living room. Skype has mindshare, and runs on virtually every platform in existence.
Sure, they have Messenger, but most people think of that as an IM solution, and zero people think of it as a leading edge platform for new innovations.
I predict Microsoft's top two goals will be:
1. Don't screw it up. They need this as a flagship consumer user base to complete their communications story, and the last thing they need is to turn it into the Danger acquisition. So no scratch rewrites in .Net or other poorly planned Microsoftization.
2. Make everything talk to each other. Lync, LiveMess, Kinect, and Skype should all be able to intercommunicate seamlessly using VOIP and video calling. Try to create a virtuous circle where each part of the network makes all the other parts even more useful.
If they can grow Lync Client/Server into as important a business as other core MS servers, they'll be printing so much money that it will justify Skype never earning a penny. If they can make a Kinect the default videophone for the living room (everyone can come sit together to talk to grandma!), they will dwarf other game consoles and set top boxes. If they can earn a default app install slot on everyone's cell phones, they can use that as a launching pad for a raft of other services (Bing being exhibit A). And, of course, if they can win in a market that Google, Apple, and Facebook also want a piece of, they are a step closer to earning back a little bit of their halo effect. The upside of this deal is totally justified.
Whether they can execute or not... that's the tricky part.
