Multiple WCF Services implementing same Service Contract interface?

Yes, it's not only possible, it is explicitly within the design intentions of service contract interfaces.

If you define IUselessService interface inside a separate assembly and place this in GAC. This assembly should don't implement anything only define IUselessService interface and some other types which use needs as a parameters of IUselessService.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.