In my case, for example, I use it to review books. Each thread includes the book's information in the first post, and the comments are reviews, so users can only vote once. For this proposal I also use [OzzModz] Thread Reply Max Posts In Thread Permission.
I also use it in another forum to rate news, but in that case, even if the article isn't well-received by readers and only has one star, I want to continue indexing it because the ratings don't reflect the quality of the text, but rather whether the user is more or less enthusiastic about the new.