Funding and outside influences aside, writing a business plan is still one of the most important aspects of developing your product. When working on an idea, if my product isn't important enough to warrant a couple days pouring over the market research and putting something together, then the idea isn't worth developing.
This is especially true if you have more than one person working on the project. You need to make sure everyone stays focused on the big-picture goal, and that everyone is equally aware of the target market and projections for the company. You don't have to get incredibly specific in the plan though. Feature changes shouldn't need to be included in updates to the plan. But if your project is changing directions or target market, then the changes should be researched and plan updated accordingly.
That being said, I almost always leave out financial projections until later in the game after v1 has been launched, because even most investors will know that this section is complete BS before that point.
Oh, and all of this should of course be filed under "IMO".
This is especially true if you have more than one person working on the project. You need to make sure everyone stays focused on the big-picture goal, and that everyone is equally aware of the target market and projections for the company. You don't have to get incredibly specific in the plan though. Feature changes shouldn't need to be included in updates to the plan. But if your project is changing directions or target market, then the changes should be researched and plan updated accordingly.
That being said, I almost always leave out financial projections until later in the game after v1 has been launched, because even most investors will know that this section is complete BS before that point.
Oh, and all of this should of course be filed under "IMO".