VCs Pay Business Plans Little Heed, Study Finds

I'm more interested in whether reality pays heed to business plans... did Google, IBM, Microsoft, Apple, Xerox, HP, Ford, Bell, Edison have business plans? Is there a correlation? Or maybe an inverse one?

The article seems to be saying that a "business plan" can help you see what the competitive landscape is at the moment. So it's not so much a "plan" for the future, but a picture of reality now.

It's similar to how I've started solving coding problems: to write down what the things are. This is not itself the solution, but it helps me to see clearly by removing so many factors, and then I can come up with a solution. I think it has a similar basis to what Fred Brooks said about complexity being easier to understand when represented as tables (objects, structs) than as flowcharts (code).

How much effort should one put into a business plan then (once the idea is solidified in their head)? Where is the point of diminishing returns? Is it still worthwhile to do a five year forecast (especially when it's highly unlikely things will go as you plan (for better or worse) over that much time)?