Before the rise of Amazon and Ebay, you (almost) always knew when you were buying a counterfeit, because you were getting a great price for the latest Disney VHS from someone selling out the back of a van at the local flea market.

The other option was to go to bricks-and-mortar retailers, where if they had it in stock and if you were willing to pay full retail price, you'd get something that wasn't a counterfeit.

Amazon seems to have pulled off some marketing magic where flea market sellers plus a refund policy equals one of the world's largest companies.