Aside from the fact that this is a looser's strategy and a proof of the dismay in which mobile operators find themselves dealing with Internet technologies this is YAGI (yet-another-good-indication) for Jajah... and of course YABI (I'll let you figure that one out) for Skype. Unless in combining strengths with eBay the latter also shifts from a device-based P2P software for VoIP to something else. The reason I think it's YAGI for Jajah is obvious: Jajah is (not only) about VoIP or at least, they do not require a mobile (or fixed) operator's authorisation to establish a call between two parties by bridging two calls they initiate from their infrastructure.
By the way, during my last trips to Luxembourg, I used Jajah for most of my calls. I am working through the complicated pricing schemes and roaming agreements between mobile operators to assess the savings (I wonder how commercial companies are allowed to have such complexity in their price lists)... Using the extra cool feature of doanloading the history of calls in Excel format that is available on Jajah, I expect to be able to assess the monetary value of savings achieved. What I can say is that the quality of sound was just excellent. So if I can get good service at a lower price, the whole deal bcomes a no-brainer even if it asks of me as a user to slightly change my education about how to place a call.