Yeah well you might be tricked at the LFS too.
I work at a LFS and I clean the feeder tanks of bodies every 2 hours or so. If you came in you would probably think our fish were safe. In the morning there is usually a pile of +100 guppies in the guppie tank and +20 or so goldfish in the goldfish tank. The other fish have a feeding frenzy on their bodies. These are medicated tanks!
An analogy would be the difference between raw hamburger meat and a raw steak. The steak is from one cow and you have a low chance of getting sick from it. Hence, many people eat raw steak. The only difference with ground beef is that it has been ran through a grinder and exposed to hundereds of cows, so it likely contains some harmful e coli. etc.
My aunt actually eats raw hamburger meat when she makes burgers and I think she is insane. It doesn't mean it is safe or we should all make a habit of it (maybe she has a tough gut, I really don't know how she keeps on living). Plenty of children died at Jack in the Box from E. Coli in cooked burgers. Many references can be found with google.
Feeder fish kept in tanks of 1000 or more fish are much more likely to be exposed to a disease. One lady I kept warning about disease (I always do this when selling them), but she insisted it was safe. One week she came in sad about her Oscar's death, none of her other fish (who didn't eat them) died. He also was only a year and half old. She was convinced at that point and now raises her own feeders. I have other customers with similar stories.
These are my experiences and why I suggest people to stear clear of them.