The Supreme Court dealt with a relatively large number of defamation cases over the years. I was curious to see which media were most commonly involved. With the help of my trusted RA, Brandon Hobbs, we were able to create the above graph based on the analysis of 45 cases found on Westlaw.

(Caveats apply: we have not carefully vetted the data and so you should consider it preliminary and there are various judgment calls one must make. Still, I hope that would be useful to others. When a case involved two mediums, the case was counted twice.)

If interested, the data can be downloaded from here.