Are Business Plans Really Necessary?

In my interview with Romanus Wolter, he took a somewhat contrarian view about business plans, saying that entrepreneurs should first focus on finding their passion and then testing their ideas in the marketplace.

What do you think? Are business plans an absolute essential, regardless of the stage/size of your venture? Should it be the first step in any entrepreneurial venture? Or are business plans merely a formality for bankers/investors? Click here to share your thoughts in the Entrepreneurs Forum.