here's some real crap:
I had an app I liked/used so much I had paid for it. There was no difference I remember between the paid and free versions, there were no ads in either. The paid app was simply a way to show you supported the work.
The programmer redesigns the app, and previous paid versions are no longer valid, all are now free versions and you get to pay again to use the ad-free version.
Asshole.