A very good way to get rated "poor" is to call someone on their wrong advice. This sometimes happens in the Finance and Tax section, where -- with tax law especially -- a little knowledge can be a dangerous thing for new immigrants.
I corrected someone, asked him to support his advice by citing the basis in Law, he preferred instead to engage in personal insults or comments, and after that I noticed I was getting a negative vote every few days, regular as clockwork, over a period of weeks. The regularity of the negative votes suggests it was him, possibly using a reminder system, rather than a random collection of readers who suddenly decided in unison that didn't like my advice.
This rating thing is so subjective, so open to abuse, that it is best ignored.