The first or second tag, sorted by popularity, that is not in the title is prepended to the title.
In your examples:
How do we maintain answer quality when everybody thinks they're experts? The top tag of the two on the question is content-curation with 19 questions (versus community-standard with 7), so it is added to the title
Advantages to storing content locally vs outsourcing it to a 3rd party small-communities barely wins on this question with 20 questions, so it is added to the title.
