Life Lesson from a Black Eye
I'm fond of arguing that Plato is the father of philosophy. Apparently that is the wrong argument to make, in a bar, with a stranger, when said stranger takes the opposing view. (And I thought politics, religion, and his mother were the only things never to discuss with a stranger in a bar.)
Contaminated / Politicized Forecasting Process
Every point in the forecasting process can be contaminated by the biases and personal agendas of process participants. One argument against overly elaborate processes (with more human touch points), is that they create more opportunity for these biases personal agendas to contaminate what should be an objective and scientific process.
Anyone with input into the forecasting process can use this input for their own benefit. A sales rep at quota-setting time will try to lower expectations to get easier-to-beat quotas. A product manager with a new product idea will forecast sales high enough to meet the minimum hurdles for new product development approval. Just about every participant will have a special interest of some sort, and these interests must be taken into account.
Elaborate and overly complex forecasting processes are also a poor use of organizational resources. Does each participant in your process actually make the forecast better, or can these participants be reassigned to more worthwhile activities in the organization? (See Forecasting or Golf?) Most people do not like having to forecast, have no training or skills in forecasting, and do not add value to the process. It may make more sense to have your sales people selling, your service people providing services, and your management doing whatever it is they do, if their efforts are not improving the forecasts.