Sales forecasting is a common activity, you need to know how much revenue is going to be generated in the coming months. Usually it is done by sales, usually by a straight extrapolation with a few adjustments, and the only thing you know for sure is that it will be wrong.
How cool would it be if your marketing people were able to forecast revenue with some accuracy?
Marketing is an investment in revenue generation, which is an outcome of demand, so it would seem sensible to focus attention on demand in the market, not what sales you did last month. Mindset is important. When you treat something as an expense, it is easy to chop and change based on short term conditions, but when it is an investment, it has longer term implications, and what could be more important than an investment in revenue generation???
To truly be treated as an investment, there must be a reliable ROI calculation that can be made, which means the collection of data, and the agreement on a set of metrics to be applied.
There are lots of tools emerging that claim to automate the marketing process, and generally they do it well, using the traditional sales tunnel metaphor connected to the marketing tools of the net. Whilst it is creating another source of operational complication necessary to get the data, it should be seen as a part of the investment strategy.
However, the mindset change is simple. Recognize that the role of marketing is to create demand, and the cost of using all the tools of branding, innovation, channel selections, and all the rest, are the costs implementing those investment decisions.