From the "whaaat?" department.
Much has been said about the ability of the Apple App Store to make software developers money. Writing programs for the iPhone is either a terrible idea (you're one of a million!) or a great get-rich-quick scheme (millions of potential customers!), depending on who you listen to. But most of the focus has been on paid apps – which generally sell for $1 to $5 apiece.
And if developing for the iPhone is a questionable enterprise, developing free apps has been viewed as downright unsound. "Give away stuff for free? What am I, an online newspaper?" But new data from mobile ad server Adwhirl suggests that applications that crack the App Store top-100 can make anywhere from $400 to $5,000 a day. Did you hear that sound? That was software developers everywhere spitting Mountain Dew all over their keyboards.
Don't go quitting your day job to develop free iPhone apps just yet (heck, it's so bad out there Microsoft is laying people off). As Dan Frommer at Silicon Alley Insider points out, "The vast majority of apps are not anywhere near the top 100, and will have the same problem making money from ads as they do charging for their apps."