Let’s face it.. getting app downloads is tough. There are over 200,000 apps out there, and it is very easy for an app to fade into obscurity.
Even free apps can suffer from this, you really have to get the word out there, and there are many different approaches.
One approach that has worked for one developer was to take their app, and release the source code. With so many people interested in iPhone development the app was able to go from 40 to about 1000 downloads in a day.
The source code will be added to the Open Source iPhone App Store Apps listing.