To keep the analogy: if you live in a quarantined clean room to protect your immune system from the bad germs, viruses etc, you're going to end up with a very weak immune system. If you expose your immune system to the world, it's going to learn how to fight specific threats it'll encounter.
And yet for the really virulent stuff -- the polio, the smallpox, the measles -- we don't rely on random exposure, we innoculate with dead and fragmented pieces of the virus while working to exterminate it in the wild.
That would be the illegal stuff, I think. We're dealing with that on a societal basis. I suppose the extent depends on the trust we place into the ability of citizens to not collectively fall for something just by being exposed. If we all had very frail immune systems, doing our very best to extinguish the common cold would make sense. Since we don't, let's keep those reasonably safe that are in danger and let the rest deal with it.
For anything else, it may quickly become problematic if those that get scared or upset the most over news stories are in charge of declaring when to quarantine people, neighborhoods or states.
