Futher to Craig's previous post on Skype and eBay have a read of this article in New York Times where Skype founder Niklas Zennstrom puts up a solid(ish) defence of his decision to sell to eBay and why the price was fair.
My take is Skype revenues are bigger than Facebooks' and Facebook is valued at $13bn so Skype is real value.
Two further thoughts:
Does the eBay write down have any financial or tax benefits?
Or is it more about not wanting to pay last tranche of cash to founders?