Should it? There's opinions people have, and what they're game enough to express in a forum / board / guest book. Down voting I don't think is absolute, it depends on the thread topic and what is being discussed. As such it might act as a guide of what the general opinion is, or it could mean the poster has stuck a sharp nerve for many who feel very annoyed for personal emotional reasons and little to do with the topic.<p>As such down voting might mean more review of why, addition research to get a better grounding if your own opinion was based more on a gut feeling or poor outdated information ... or it could be the opposite.
It's a flawed system now that people most often use downvotes as disagrees. In the process of disagreeing you are also suppressing alternative opinions and information. It's the modern day version of shooting the messenger. Slashdot figured this out in the 90s. If you're going to ask people to rank stuff you need to give them a handful of basic categories to choose from (inaccurate, misleading, redundant, etc) instead of a good vs bad binary selection.