OK, James Surowiecki sees the Wisdom of Crowds. But then Bryan Caplan noted that the average voter is irrational. And of course Philip Tetlock notes that experts are usually wrong. So you think all is left is models, a simple equation? Well, not for inflation forecasting. From Geert Bekaert's forthcoming article in the Journal of Monetary Economics:

We examine the forecasting power of four alternative methods of forecasting U.S. inflation out-of-sample: time-series ARIMA models; regressions using real activity measures motivated from the Phillips curve; term structure models that include linear, non-linear, and arbitrage-free specifications; and survey-based measures. We also investigate several methods of combining forecasts. Our results show that surveys outperform the other forecasting methods and that the term structure specifications perform relatively poorly. We find little evidence that combining forecasts produces superior forecasts to survey information alone. When combining forecasts, the data consistently places the highest weights on survey information.

So, as a rule, there seem to be no rules for when picking which class of forecasters to pick from.

Perhaps Nassim Taleb is onto to something: say 'something unexpected will happen', and then, when something unexpected does happen (which by definition no one predicted), point out your prescience. Brilliant!