- How are you going to make money? What if that revenue model doesn't bear fruit... any other ideas?
- How are you going to reach your customers? How much will it cost to reach your customers?
- Roughly, how big is your market? Is there a lot of demand?
- How big a team do you need to test your initial theories and roughly how expensive is that going to be?
- Are there any other significant expenses aside from people?
- How many sales/pageviews/whatever would it take for you to be cash flow positive?
I don't good investors ask these questions to test your planning powers... I think they ask them to test how smart you are and how much you've thought about this stuff.
Being able to toss out some ideas on distribution/marketing is different than having a 2 page section on marketing. Being able to say that you need two more devs to build what you think you need to build in the next 12 months is different from having a 4-stage hiring plan with assorted milestones. Tossing out some ways you could make money is different than a 5-year revenue projection.
I don't think those questions aren't asked because you should have a confident answer to any/all of them. They are asked to confirm that actually think about the issues in question.
It's like agile development vs. waterfall development, IMO.