I followed the Recon Ron program for several months -- I got up to doing 15 deadhangs in the first set (of five). The protocol works. (It's not a pyramid, by the way; it could be described as a half pyramid if you want to classify it -- the highest number of reps comes in the first set and they decrease in the following sets.)
There is no question that one could follow the program ad infinitum adding more and more pullups. As I recall, the version I saw was 38weeks long and got to 31 pullups in the first set. There is also a shorter version floating around the internet. Here's a WFS link to the longer version: http://webpages.charter.net/bert/reconron.html
Overtraining, though, Chris? I seem to recall a serious challenge to reach 50 pullups in one set on this message board a year or two ago and that several posters reached that goal. It all depends on what you want and using common sense to get there.