Kind of - you can remove the association of "contact" (in your phone) to the "friend" (on the social network). There's no way to undo any changes applied to your contact once you've exited Hermes: if information got added to the contact that you didn't want, you'll have to remove that your self (or load a backup if you have one).

To remove the association, open the address/phone book, find the contact and click the photo to start edit the details. At the bottom there should be "web link" looking like http://www.facebook.com/....... - you basically remove that contact field and the association is gone.