Pagejacking does not mean taking over a page on the original site. In fact, the original site can be completely unaware that the theft has occurred.
Pagejackers siphon off traffic indirectly though the search engines. The stolen pages are copies or near-copies of the original pages. The stolen pages are then submitted to the search engines in an attempt to duplicate the rankings of the original pages. After the pages are submitted, the stolen pages are switched in favor of pages which earn revenue for the thieves. To further complicate matters, sometimes cloaking is involved.
While very large, elaborate schemes have been uncovered, pagejacking is not the sole province of the technically proficient. Many would-be-thieves are of a decidedly low-tech variety.