If you google
rails barcode scanner with the filter to only display results from the last year, the top StackOverflow link is the post below:
A thoroughly unhelpful, closed post with one poor answer and a comment advising the user to google the solution before posting and asking for help. Ironically his useless post became the top result. I'm not an expert on page rank, but I imagine it's possible to manipulate meta tags, links, etc. to discourage search engines from pointing to low value content.
What if unhelpful, closed, extremely down-voted posts were somehow un-tagged to prevent them from appearing in common searches?