I know that the rules state:
In order to ensure visibility and enforcement of these Rules, you may not use a single application API key for multiple use cases, and you may not use multiple application API keys for the same use case.
What exactly is meant by a “use case”? We are building an app that will allow you to share posts to Twitter. There will be an iOS version and a web version. Do we need to use different API keys for web and iOS?