Couldn't Black Hat
SEO be used to de-rank a competitor. For example, if someone is ranked above you for a search term; couldn't you just use black hat
SEO to pump their site and then get them downgraded on the search engines?
I just wonder what stops people form doing something like this to remove those above them in the results. I would fear a competitor doing this to me and my 76+ number one rankeings for Sacramento web related results.