Both of the possibilities you list involve CBS being duped. I don't think they were duped at all. Rather :=) than that, I'd propose they were willing participants in a deliberate fraud.
CBS and Rather were not interested in authenticity. They wanted to get something out there to stop Kerry's bleeding in the polls. The were wong, wong, wong.
It looks to me like the DNC has successfully taken the Swift Boat Vets off the front page, and if/when any documents arise regarding John Kerry's service records, the DNC will just say, "Those are obvious forgeries." "Now can we just get back to the work of the American people. The American people need jobs and health care . . ." John Edwards alluded to such this morning or last night in some news account I read.