Do you see the blue bars on the graph? That's ad revenue that Flurry have been tracking. Note that it peaked in December 2009 and has been flat for most of 2010. Even though more people use apps, the ad revenue isn't going up. Consider how this applies to magazine apps.
We have companies investing hundreds of thousands of dollars in apps while the ad market is flat. I don't know about you, but this feels more and more like the tech bubble.