The Black List or the Ban List is the list of the Internet sites which are using incorrect means of promotion.
Such ways of a site promotion are targeted only at artificial increase of site ratings and corruption by search results, and don't take into consideration interests of visitors. As a result, the site temporarily arises in a provisioning on the necessary search queries.
"Tap" of competitors is one of the widespread ways of a site violations detection. If the commercial site violated the rules of search systems is found in the top tens of search results, the competitors quickly report search systems about it.
After the search systems or their administrators reveal violations, the site not only leaves the first pages, but often it's forbidden at all for search by engine indexing.