Numbers for Digital's Rise（数字化增长数字）

I talk a lot to people who don't quite understand the scale of the media shift from atoms to bits (update: corrected), so I always have my eyes open for numbers and anecdotes that illustrate the point. The latest I found are from an article on Apple's threat to shut the iTunes store if it has to pay more to songwriters:

Digital downloads grew 38 per cent from 2006 to 2007 to become a $1.26 billion business, making up 23 per cent of the market for recorded music, according to the Recording Industry Association of America. Sales of physical music media such as CDs, cassettes and DVDs declined 19.1 per cent to $7.5 billion in the same one-year period.

I'm still looking for convincing numbers on film and TV movement to digital. For example, does anyone have numbers on how well Dr Horrible's Singalong Blog (the web-only offering from Buffy creator Joss Wedon) did?