Say everyone in the world stopped pirating music, the effect this would have on sales is debatable. Some people say musicians would sell more because people who previously pirated their music would have to buy it instead. I’m not convinced by this argument. I think that the majority of people who illegally download don’t make a choice between paying and pirating, they make a choice between pirating and not listening.
So while you may make some extra sales, you’d also lose some listeners, and potentially their friends, and their friends, and so on. If someone can’t afford my music, I’d much rather they pirate it than just forget about me. But if they do pirate it I would hope they’ll keep that in mind and try to help me out in other ways - an obvious example is telling other people about me, which may end up in a sale I wouldn’t have made otherwise.
It’s a complicated issue, and I can see problems with this approach - you don’t want a generation of kids growing up thinking it’s alright to just not pay for shit. But I’m hopeful that a closer relationship between artists (especially independent ones) and fans, one that youtube and social media has allowed us, will play a part here by making people WANT to pay for music because they want to support the musicians they like. When your £10 goes straight to WMG’s bank account, who really gives a shit? But if it goes straight to the artist, you know that it’s genuinely making a difference to their life and a good portion of it will probably be used to pay for their next record.
However, the important thing to realise is that this has nothing to do with SOPA, it’s a totally different discussion. The main problem with SOPA is that it says websites should be responsible for everything their users upload. So if one person uploads a cover song to youtube, the whole of youtube.com can be taken down. That’s so ridiculous I don’t think I need to go any further. But if you’re interested, here’s a TED talk on the history of SOPA/PIPA.