I've been trying similar-style videos on advanced data analysis/visualization since such screencasts are an unexplored area (my most recent video using Stack Overflow data: https://www.youtube.com/watch?v=6OeyTfp7eq8) but there are a few snags which make it less accessible for anyone to do:

1. It requires subject preparation to avoid going off on a tangent. (in the case of the video above I cheated and use prewritten code, and the video was still 30+min long.)

2. It requires specialized software and hardware that's not free. (good recording software + good mic + good webcam are $50-100 each)

3. It requires good hardware preparation too (e.g. precise placement of the mic and good light for webcam, so I couldn't record at night)

4. It requires time for editing (unless in my case you slap on background audio and call it a day)

I bought a new mic since I was unhappy with the audio quality in that video, and am taking steps to refine video focus.