Half, Not Half-Assed
Build half a product, not a half-ass product
Beware of the "everything but the kitchen sink" approach to web app development. Throw in every decent idea that comes along and you'll just wind up with a half-assed version of your product. What you really want to do is build half a product that kicks ass.
Stick to what's truly essential. Good ideas can be tabled. Take whatever you think your product should be and cut it in half. Pare features down until you're left with only the most essential ones. Then do it again.
With Basecamp, we started with just the messages section. We knew that was the heart of the app so we ignored milestones, to-do lists, and other items for the time being. That let us base future decisions on real world usage instead of hunches.
Start off with a lean, smart app and let it gain traction. Then you can start to add to the solid foundation you've built.