I've updated my edited version of the United Nations Registry
of Space Objects, at 
 http://hea-www.harvard.edu/~jcm/space/un/un.html
Member states of the UN are required to register space objects
owned by them; the accuracy and completeness of the information
provided is pretty spotty. The United States remains the
state with the most errors and omissions in its submissions;
Mexico, Germany, Australia, and Brazil are grossly overdue
in updating their registrations. The US should be registering
INTELSAT's satellites, but does not; the United Kingdom should
be registering INMARSAT's satellites, but does not. 
Since 1991, when the US last failed to register one of its
classified satellites, there is no evidence of any state deliberately
failing to register a satellite to avoid detection - the omissions
seem to be due to sloppiness.