The EFF have an interesting investigation into WSJ and Al-Jazeera ‘leaks’ sites and terms and conditions which suggest users’ anonymity is anything but protected:

“Despite promising anonymity, security and confidentiality, AJTU can “share personally identifiable information in response to a law enforcement agency’s request, or where we believe it is necessary.” SafeHouse’s terms of service reserve the right “to disclose any information about you to law enforcement authorities” without notice, then goes even further, reserving the right to disclose information to any “requesting third party,” not only to comply with the law but also to “protect the property or rights of Dow Jones or any affiliated companies” or to “safeguard the interests of others.” As one commentator put it bluntly, this is “insanely broad.” Neither SafeHouse or AJTU bother telling users how they determine when they’ll disclose information, or who’s in charge of the decision.”