Why does Schiphol Airport have such a long taxi?
Schiphol indeed seems to have enough space to build a runway close to the terminal. However it is more the lack of airspace and laws preventing excessive sound levels that made it necessary to create the "polderbaan". It is also one of the two primary runways for nightflights (link in Dutch (sorry). Found a reference in the English wikipedia:


  Newest runway, opened 2003.
  Located to reduce the noise impact on the surrounding population; aircraft have a lengthy 15-minute taxi to and from the Terminal.