Why should you be open about your start-up business model?
Over the years, I've noticed an odd rule: when I met entrepreneurs who will not tell me anything about their business idea, I generally do not see that business becoming successful. On the other hand, many successful businesses have been very open about their strategies and plans.
I can't remember the number of times I've met people who say words to the effect of "I'm launching something in the 'x' space, I can't tell you anything more about it, but you'll know all about it next year", and then I never hear from them again.
I think that this is primarily because if you do not tell anyone what you are planning, you don't open yourself up for constructive critisism. Particularly if you think you have a great idea that no one else has thought of. There are very few of these ideas around, so it is much more likely that someone (or several people) have tried it and failed, or just dismissed the idea after some research - you won't see anyone else doing your idea, but not for the reason you think. You also miss out on advice and suggestions that could improve your business.
Generally successful startups are in growth markets and a number of similar companies will be launching at the same time: if not, I'd be sceptical of the quality of the idea, and it's also worth bearing in mind that launching a brand new concept is very hard and you'll need to be very well funded. Why is that? Basically because competitors grow the market by informing more people that your type of product/service exists and create a demand for it. It is much easier to sell to someone who is already saying that they need, say, shared online workspaces than it is to explain what one is to someone who has never heard of them and then sell it to them.
Obviously there is always commercially sensitive information, and you have to know where to draw the line, but you don't have to be totally secretive.