Though of course it becomes a problem when wild numbers of clownfish and regal tangs begin to decrease in the wild, all because of wild-catching them for the pet trade to supply demand produced by so many children wanting them as pets because of the movie.
The vast majority of the clowns in the pet trade are tank bred. They are among the very small number of marine fishes which have fry that are large enough to take easily obtainable foods (others include many seahorses and Banggai cardinals). The situation with regal tangs, powder blue surgeonfish etc is as you describe.
I have seen meerkats in petshops too, but I'm sure these were also captive bred.
Alan