> you'll need to do a lot of quality work to prevent mediocre results from a boosted site from shadowing better results from unboosted sites That strikes me as

> you'll need to do a lot of quality work to prevent mediocre results from a boosted site from shadowing better results from unboosted sites That strikes me as a non-goal. As the search engine, you can't know what attributes a user is valuing when they boost, and so you can't know when it's appropriate to override that boost. "Better" is subjective, contextual, and comes in thousands of different flavors.