Usually when you see animal hoarders on TV. They usally live in trailer parks or equivilant, haven't showered for days, and there is animal mess galore around and in they're abode. So your looking for someone with 100 plus 10g tanks with no filtration. That would weep like a baby if you took any of his/ her fish away.
I think this depends first on if someone is a hobbyist or a professional.
I wouldn't call someone with a fish room or a store a hoarder. Both of these will have crowded tanks with fish waiting for sale or breeding tanks where they are raising fish that will be sold.
Maybe some hobbyist depending on the number of tanks, type and number of fish in these tanks could be considered hoarders. Not that having many animals is always bad. Some people can handle it.