This post from tnl.net, entitled Where the hits are streaming in 2011 was a real eye-opener, and one that I first heard on TWiT 336.
For each movie of the top 100 movies at the box office, I pulled data on for streaming info on Netflix, Amazon on Demand, iTunes, and Vudu. I also pulled up availability of DVDs to use as a yardstick in terms of overall movie availability.