Nick Paumgarten's piece, "The Secret Cycle" in the 12 October 2009 New Yorker is probably worth a read for some readers of Broken Symmetry. The article, which is unfortunately gated, retells some of the history of technical forecasting based on observed periodicities in a variety of independent variables, including (naturally) market prices.
Armstrong sounds like an idiot savant to me. He probably is quite good at the technical analysis, but is full of @#$# when it comes to his speculations about what mechanisms might account for observed periodicities. So are most people who claim to see signal in the noise of market prices. For the record, your author endeavors to invest only with a margin of safety calculated Graham-and-Dodd-style (or, better, Buffett and Munger-style) from fundamentals.
But long-time readers of Broken Symmetry may recall earlier posts on a "fundamental hypothesis of periodicity." Also for the record, I will say that I believe there are probably collective modes of oscillation produced by organizations of individuals that arise from weak nonlinear couplings of human behavior. That belief is not pure speculation, as the papers from Malmgren and Watts and on synchronized clusters demonstrate.
I am profoundly skeptical -- in fact, I believe it's impossible -- for us to accurately forecast market price cycles out for years into the future with day-level precision as people like Martin Armstrong claim to be able to do. Yet I believe it's not impossible that much more of our social and economic lives are governed by low frequency, but large-scale and low-magnitude "forces" than most economists would admit. It's just that the higher energy noise of everyday life makes the influence of these weak forces much harder to discern. It's only in moments of profound social uncertainty -- such as the present crisis -- that people begin to wonder how much of their individual destiny is truly independent of their neighbors'.
Robert Musil says somewhere that we are as connected to each other as two drops in a river. That has always sounded about right to me. And if you're thinking, "That's not too connected!" then I refer you to consider the chemistry of water more carefully (and particularly the hydrogen bond), and remind you that Musil was trained in that chemistry.