Ok - so there have been lots of rumours and the Independent have added to these with a brief article where they claim News Corp made an approach to Skype that valued it at $3bn and that the negotiation "broke down last month".
Skype currently claims nearly 150m downloads. If you take a 10% active-user rate (which i think is probably very high), that gives Skype 15m active users, the majority of which are using the free VOIP element, not the fee paying parts of the product SkypeOut and Voicemail. Even assuming 15m active, the NewsCorp bid puts a per-user valuation at $200, which Ok doesnt sound a lot , but its probably at least 100x average per-user earnings.
Skype is a great product, but its not the only product in this space. I'm sure the company has some very grand plans, but history shows how a market leader can be quickly overtaken and surpassed (netscape -> IE -> firefox). A $3bn valuation is flattering and I suspect it respresents an extremely good return for Skypes early backers who include Morten Lund and Ariadne Capital, and their Series A backers who included DFJ, Index, Bessemer, and Mangrove. Im sure there is some truth in all the rumour, otherwise its an incredibly well executed PR campaign to seed the idea of a sale. Either way, i think a sale will be tied up by Christmas.
update 12/09 - Ebay has acquired Skype for $2.6bn - phew! press release here