I know this was for Noobdog, but I thought I'd chime in..
Business models and plans, at least for me, are a good way to focus on your goals. I like getting down on paper what exactly I want to accomplish and the path to get there. I would think that if you are looking for investors that having a plan would be reassuring. Also, I find it easier to identify flaws in my plan if I "brainstorm" on paper.
My partner and I have done this a bit, writing down what kind of company we want to be and the like. As I continue to read and learn, jotting down ideas and steps helps overcome the tendency to forget something 2 seconds after it dawned on me...LOL.
I've been in businesses that had a plan and/or model and I've helped develop a couple. It's pretty easy and doesn't have to formal, just what you'd like to accomplish and steps you need to do so.
Let's say my goal is to buy a house. My plan is to clean up my credit, save money for a down payment, nail down the neighborhood I'd like to reside and find a house....etc.
Or, let's say I am starting a business. My model is how I would like to structure that business. Am I a sole proprietorship, or do I have partners and/or employees. If I have employees, what are their responsibilities and how does the hiearchy play out? Does it make sense to outsource certain jobs? What kind of reputation do I want my business to have? Am I a retailer, supplier, wholesaler, distributor, consultant, seller, investor, etc. What are my projected earnings at year 1, 5, 10..?
If you google sample business models, you get a slew of information.
Disclaimer: The above is how I see it. I'm convinced these things are open to interpretation and personal need/preference.