Don't Give Customers What They Want, Listen to Their Problems

Don't worry about scaling until you need to. No one ever gets it right on the first shot. Don't shy away from monotizing your products. There's a whole bunch of tools now that allow you to take mock ups and make them clickable. But initially, ah, you need to make sure that your product is working for people. And then expect that however many iterations you think it will take, expect it'll take 10 times as long.