Chel-
I think you have a good point, but not a scary one. I just spent a while looking at articles that pertain to bird flu transmission, and have an idea to add in regards to your post. The way that flu seems to get from birds to people a bit graphic; direct handling of body parts or fluids from infected birds, and inhalation or ingestion of the feces of infected birds. This suggests that the super-clean environments that most people who show birds or even just keep small flocks maintain is perfect for avoidance of transmission by feces. Likewise, the daily contact and familiarity with show birds or small flocks would go a long way towards avoiding contact with sick bird fluids; I would argue that if your bird got sick, you'd know very fast, seek more information, and so forth. You probably would not slaughter it and ingest its uncooked blood (the way that bird-human transmission occasionally occurs in SE Asia).
The big scary thing that may be driving bird flu movement that I just learned about is poor washing practices in farm equipment; like muddy-feces covered truck tires, or containminated feed. To avoid this as a potential spreading method to your flock, though, is easy! Keep your vehicles, clothes and shoes clean, and buy from clean and good reputation food suppliers. I think that is common sense for all bird diseases, so it should not be something that anyone would balk at.
I have a tough time imagining this scenario, but here it is; someone at a bird show brings a chicken with a bad case of the sniffles. They track its feces around the show on their dirty shoes. You get those feces on your shoes. You go home, walk to your coop in the same shoes, and inadvertantly spread the germs into your backyard. Your chicken taste-tests the dirt as usual, and ingests the feces. They get sick. The rest of the flock catches it...
But remember! The vast majority of bird flu is- BIRD flu. Not people-bird flu.
You are SOOOOOO much more likely to get in a car accident. Or have a heart attack. Or have raccoons raid your coop. Or stray dogs. Good lord, it is a wonder we all survive in this world at all!
-MTchick