I've been experimenting with the UnsafeAuthenticatedConnectionSharing setting in order to speed up the WebService call time. I must say that the results are quite satisfying for the time being. Going from several seconds to sub-second response time. In our solution the service gets called about 60.000 times in a row so performance is a key factor in the process. Obviously there are some downsides to this property. Make sure you carefully study the security aspect before implementing this. In our case it is an application that uses just one user account and runs on a server without user intervention.