I only know about a non-LaTeX solution using PostScript. Because PostScript is a programming language it can randomly pick fonts while typesetting a text. A program ransom.ps using that effect was once posted on Usenetpublished by Diomidis Spinellis on Usenet. The description reads:
This is a small postscript program you can use to create ransom notes. Enter the text you want between the brackets at the beginning of the script and send the whole file to a postscript printer. The text will be printed using many different fonts, sizes, orientations, and styles. You can modify the margins and the fonts used, by modifying the source.
Executing the PostScript code ransom.ps gave me the following result:
