it seems to work out with advertising, as it is for more and more app developers because you just get so much more installs without a pricetag on it. Most devs dont have any marketing muscle, so free apps with advertising often is a good approach.

Do you do any marketing/promotion at all, or just stick your Apps up on the Market?

You do the best you can with the resources you have to promote your app, even if its free, since that cant hurt. Even with free apps you still need a good app and luck, its not that any free app will generate tons of ad revenue.

Simplicity and risk exposure. He's clearly doing quite alright with ad-driven applications.

I doubt he'd get higher profit with paid apps.

Nice answer, and makes sense, but was that last line really necessary?

Parent sounds like genuine curiosity and not condescension, and when in doubt, be charitable! :-)

Feedback executed.