the same rationale used by all governments to conceal evidence of their wrongdoing: we need to suppress our activities for your own good. WikiLeaks is devoted to subverting that mentality and, relatively speaking, has been quite successful in doing so.
For that reason, numerous governments and private groups would like to see them destroyed. Corporations have sued to have the site shut down. And in addition to this 2008 Pentagon report, WikiLeaks has acquired, though not yet posted, other U.S. Government classified reports on its activities, including a U.S. Marine Intelligence Report and an analysis prepared by the U.S. military base in Germany, both of which speak of WikiLeaks as a threat. Moreover, the FBI has refused to provide any information about its investigations and other activities aimed at WikiLeaks, citing, in response to FOIA requests, national security and other excuses for concealing it.
via salon.com