My guess is that the beardies all came from some large scale mid-west breeder and were sold to a chain like Petco or Petsmart.
I too am guilty of forgetting to wash my hands from time to time. But now that I have a 3 month old baby in the house I'm very careful.
People forget that reptiles aren't the only animals that can carry salmonella. Dogs, cats, fish, birds, etc. can be carriers as well.