[johnnyanmac]

I wouldn't call Naptster simple just because it's P2P. And P2P is in fact way more complicated and difficult to do right than a dedicated server. I hope I don't need to describe every disadvantadge and why even Spotify decided to stop using P2P (which isn't purely a control move).

[naasking]

It's simple now because it's effectively a solved problem: your client just uses one of the many robust P2P protocols available.