I take https://drupal.stackexchange.com/questions/16699/what-are-some-of-the-key-changes-to-drupal-code-for-d6-vs-d7-modules as example, but this question is valid for other questions.
The FAQ clearly reports the following text:
Your questions should be reasonably scoped. If you can imagine an entire book that answers your question, you’re asking too much.
While the question doesn't require an entire book to answer it, there are many pages on Drupal documentation that documents the difference between Drupal 6, and Drupal 7.
The question is rather subjective, because it asks the key changes without to specify for who: If a user creates themes, then the keys changes are about themes; if the user creates modules, the key changes are about creating modules. Without to specify exactly which key differences, the answer would be a summary of what reported from Drupal documentation, as the OP didn't say to which key differences he is more interested.
Questions should be more scoped, to avoid answers that would be too generic, which would then be equally valid. If I answer saying the differences for a theme developer, and somebody else answers saying the difference for a module developer who doesn't create modules for new content types, both the answers would be equally valid, as both would report the differences between Drupal 6 and Drupal 7.
Questions were the answers are equally valid should be avoided as for what reported by the FAQ.