One thing we could do, and maybe I will, is calculate the best year of the record industry sales-wise to the worst year piracy-wise. Without doing the math, I can guarantee that pirated copies of music have outpaced sales exponentially.
This would do a few things. First, it would blow a hole in the fallacy, "every illegal download is a lost sale." It would also give us an idea of how many people are actually willing to pay for music. That's really the rub, I think, people have such a glut of options in terms of what to spend their money on that they prioritize. Factor in the economy, and the ease of pirating a song compared to other media, and you have a perfect storm for why it's so ubiquitous.