The case we are talking about is a Craig's List ad selling their adult birds before they box them up to go to Canada for processing (read "made into soup").Cass, I'm new, but yesterday I did see a thread with pictures that someone did just that because they had an eggeater. If I find it I'll post it.
The rule of thumb I use regarding adult birds is to never obtain them from anyone I don't trust with my birds lives....because that is just what you are doing....an adult bird can be a carrier of any number of diseases that your flock is not immune to and wipe out your entire coop's population (minus the new birds, cuz they ARE immune) I have added adult birds to my flock, but I trusted the person I got them from. And history has shown my trust was not misplaced; all my birds are still alive and thriving. If someone is giving away adult birds they may well be doing so to start over because they have an egg eater. Do you really want to save money on obtaining your flock only to not get the number of eggs you should get because one of the "free" birds is an egg eater?