IP has the ability to draw huge, disproportionate returns. A piece of music, a book, a video, a formula, any of these can fetch an incredible amount of money if it lands at the right place at the right time. The dot-com boom provided such a time and place, and the Web 2.0 movement is doing it again.
One simple reason: it is impossible to price IP! And so it gets priced on word-of-mouth, on momentum, and on herd mentality.