It was not worth 2B for Ebay, it may be worth 8B for MSFT
Ebay had no use to it. Kapalu Charshi haggling is much better done via messages instead of in-person.
Microsoft has _LOTS_ of use to it.
The cellular networks are at a turning point. Up till now voice, video, etc were all tightly integrated into Layer2. With LTE it all goes IP. However in theory the operators are supposed to start controlling everything via IMS and enforce using the relevant Evolved Packet Core functionality.
This gives the phone OS and phone vendors the option of "My Way or the Highway".
If a phone is to do voice over LTE it will have to do IMS. If it does IMS, everything - media, applications, breath in, breath out goes under operator control. Nothing of importance will be controlled by the user or the OS vendor. The phone vendor and the phone OS vendor will see diddly squat in revenues as the billing will become 100% operator centric and they need that money to recoup infrastructure and license investment.
That is why Google keeps investing into Google Voice and Apple invested into Facetime. Microsoft has no such investment. When the day comes and LTE arrives it was largely expected to cave in and go the "My Way". In fact a lot of people in Nokia (especially in the NSN part) all the way to VP level were quietly salivating at the perspective of MSFT contracting the IMS bug through the Nokia aliance. Here is an answer to them. Balmer showed them exactly what does he think of that idea and exactly how much does he value the option of having full control.
Unless Microsoft builds a framework for voice or buys one it can pretty much forget about any revenue from Windows Mobile except basic licensing. IMO that is worth _WAY_ more than 8Bn.
Now will it work and will MSFT be able to deliver on it is another matter. However as far as the business need - it does have it.