Popular Culture?

Define "popular culture"?

In this day and age, that seems a lot harder to do.

Considering that for most of the 20th century, there was a dominance of popular culture by certain mediums:

In the early 20th century, radio, newspapers, and movies tended to dominate. In the mid to late 20th century, television dominated it.

Sometime in the 1990's, the popular culture started to fragment, starting with the rise of the Internet and satellite tv (100's of channels, all at the click of a button).

Nowadays, what people think can be influenced in hundreds of different ways. Unlike 50 years ago, it is no longer controlled by three television networks and the local newspaper.

I'm not saying there isn't a popular culture. What I am saying is that it is significantly harder to use case studies to draw conclusions over the entire culture. We have more "pocket" cultures today than we have had in the past.