If you're releasing a new product, by definition your customers won't have seen it before. Trying to calculate a solid figure for users/buyers and conversion rate is always going to be a work of guesstemation. The learned tomes, agree on this and then say it's the working used to arrive at the figures that's important. We all know the figures are fiction, but at least if it's logical fiction that shows a bit of business acumen we'll politely ignore that particular elephant in the room.
However, I was wondering if anyone has actually followed up the figures from the Business Plans of the common startups and done some research on how correct they turned out to be. The core figures normally show $50m turnover in year 5, and a big jump in profit in year 3. Other than that are all the BP figures lost, how many customer did Hotmail get in it's first few years? What was the take up of blogger - does anyone know the answer? Does anyone know where to ask the question?