Shawn Blanc writes about how to sell your app to bloggers:

Good marketing gets people to show up the first time; a good product will get them to show up the 2nd time and the 3rd time.

Really, this applies to selling anything. Marketing isn’t a vertical separate from the product. They are one. Marketing is an extension of a great product, which strings together the story of why it’s great to entice people to use it.