The community manager of Pandora just tweeted this:

First off: wow. That's a lot of stations. Even considering that creating a station is as simple as a search and a click

Second, though: Compare the 640,000 created for Whitney in 2012 to the 500,000 created for Michael Jackson during the two days following his death in 2009. Part -- actually, most -- of that discrepancy is due to the simple fact that Pandora has many more users now (over 125 million, to be exact) than it did in 2009. But part of it, too, I think, has to do with a quality users are embracing as much as the quantity they represent. It's about the increasing accessibility of creativity, about the growing impulse -- enabled by the generative power of the Web -- to convert our emotions into artifacts that can be enjoyed by others. It's not just that more of us use Pandora; it's that it occurs to more of us to use the service to create something meaningful with it. Cognitive surplus, in the service of nostalgia.