I also have a similar problem, an update of SKYPE shows up on app store and i don't have the app installed, when prompted to enter password the account is "igis8x@hotmail.it" but everything else is with my own account...
should i be worried?
I have the same email address and also Skype appears in the App store as an available update even though it's not on my iPhone.
I don't think the phones are hacked but someone didn't crack the .ipa properly and left their email address in the app. This is just a theory I am glad it's not on my iPhone 3Gs but a friends 3G iphone