Not only did this development disrupt the music industry by making songs that previously required payment to acquire freely accessible to any Napster user, it demonstrated the power of P2P networks in turning any digital file into a public, shareable good. For the brief period of time that Napster existed, mp3 files fundamentally changed as a type of good. Songs were no longer financially excludable – barring access to a computer with internet access – and they were not rival, meaning if one person downloaded a song it did not diminish another user from doing the same. Napster, like most other providers of public goods, faced the problem of free riding. Every user benefits when an individual uploads an mp3 file, but there is no requirement or mechanism that forces all users to share their music. Thus, Napster users were incentivized to let others upload music without sharing any of their own files.