First, an example of why you want to use somebody else's computer account: David Betz posts on a Guardian article describing how a graduate student was detained for six days on account he was researching al-Qaeda's tactics.
Second, Kim Andrew Elliott reminds us why we should use security filters on our laptops:
Fear of Aljazeera. A Syrian-born American who teaches at Brno’s Masaryk University was detained for 20 minutes by Czech police after a passenger on his bus noticed him revising, in his laptop computer, a paper titled "Al Jazeera and the Decline of Secular Ideology." The Prague Post, 21 May 2008