I think this is a tough topic. You have to go into a store educated to begin with and not just accept what has being delivered. I know a couple lfs that would dump something off on someone just because they don't want risk losing it in their store.
For the most part I do not buy fish from the chain stores, but there are exceptions to the rule. I picked up 5 Ctenopoma acutirostre from PetSmart for like $40 when the lfs down the street from me was selling them for $15 and $18 a piece.
As far as the workers go, you do have to be careful, I will admit that. Once again, use your better judgment and decide for yourself if they seem educated or not. I worked at my local Petco for 6 years in high school and college, and I will admit that I was the minority by already being knowledgeable in the hobby, but not everyone is uninformed.
Bottom line...you have to think for yourself.
