James Savage, in his developer blog, A Devlog, on the importance of choosing the right name for your Xcode projects:

For example, a name that can easily be changed doesn’t give me a lot of pause, and this fortunately covers most of the type, property, and method names in a project. It’s always great to choose good names upfront if possible, but sometimes things change, and that’s what refactoring is for. Similarly, names that exist within some sufficiently narrow scope (like a private repository) really only need to make sense to their author. It’s the names that can’t be changed that I worry about.

Xcode helpfully illustrates this duality by asking for both a product name and a bundle identifier as part of its new project form. While it’s tempting to think that the product name matters more here (that’s an app’s brand after all) it’s really the easier of the two to actually change. That’s because, unlike a marketing name, an app’s bundle identifier becomes permanent once submitted to the App Store.

Helpful guidance throughout for all Apple developers.

(In making his point about the immutable nature of bundle identifiers, Savage reminded me of something I’d completely forgotten: the official X/Twitter app was originally created by a third-party developer before being acquired by Twitter in 2010, which is why its bundle identifier remains com.atebits.Tweetie2, betraying its origins as an independent app.)