To be honest I feel like it's only a matter of time until they add cross-server friendslist, which will inevitably lead to cross-server linkshells and free companies. Though it's not the same as having the person on the same map you are outside duties, I do feel like eventually we'll be allowed to visit other worlds with our characters as "guests" (as in going to a different server but not being able to use it's markets or trade with players) and our "home" world will be just for the housing and market preferences.

They hinted a couple times on interviews an interest on cross server activities such as linkshells and free companies. It might suck to have blocked servers now, but I have the feeling it won't be an issue in the (near??) future.