Napster is one of the two or three products that spawned a completely different world, entirely tossing established and antiquated rules on their head.

Of course, very directly, Spotify would not exist without Napster.

But a step further, it opened the eyes to end-users about their collective power, and the beauty of distributed distribution. It was the first proof that "regular" users would buy into such a thing. Napster, in many ways, gave birth to BitTorrent, Bitcoin, and all of the derivative work thereof.