There is a certain webmaster who's currently hijacked a lot of niches with his one or two domains but 100's of doorway pages all linked which is how he gets a good placement.
I spoke to a friend of mine who's an SE guru and his only advise was to complain to Google giving as many details as possible to get them deleted but.. He added, it would take 3 months for them to vanish
So none of us can do anything unless we operate in exavtly the same way...