Hello, Omnigraffle. I bought this on iPad, used this something like, three times before having a need to use it over a year later and "Sorry! There is a new version to buy and your version is no longer supported, or runs!". It wasn't cheap, as apps go.
Never, ever buying anything from Omni, ever again.
Edit: To add details, I bought this for £35 on iOS 7. When iOS 8 came around, it was discontinued, left to crash on open, and you had the "opportunity" to buy version 2 all over again.
It's one of the most polished apps around. You don't owe the Developer's time indefinitely from one $5 purchase, and you're free to move to an alternative. I'm happy to continue to support the apps I love -- they generally aren't asking a whole lot.
Additionally, in the case of Twitter clients, they also can't add a lot of new customers b/c Twitter has capped their allowed clients. If they didn't charge customers again, they wouldn't be able to sustain the work with new ones.
- apps which were abandoned
- apps which were replaced by a successor. In the absence of update fees, this is the easiest way to generate new revenue for continuous updates. I am happy to pay for app maintenance, but this scheme means, that there is no automatic data migration from the old to the new apps.