you build something users want but can’t figure out a useful business model – users won’t pay, won’t click on adverts, etc. (no market). You build something people want, but there are just not enough users to reach profitability (small market). You build something users want, but reaching them is cost prohibitive (hard to reach market). Finally, you build something users want, but a lot of other companies build it too, and so it is too hard to get customers (competitive market).
