R. Williamson and R. Duncan's inference in their Commentary recommending DNA testing (Nature 418, 585–586; 2002), that governments can be trusted throughout people's lifetimes, is demonstrably false. Their proposed independent DNA database and laboratories could be safeguarded against many, perhaps all, misuses, but could never be protected from coercion by the state.
In the recent past, homosexuality was illegal in the United Kingdom and being a Jew was illegal in Germany. Neither of these attributes is deducible from someone's DNA, of course, but it is not outside the realms of possibility that, in future, traits that have been declared 'illegal' could be detectable in this way. Names and addresses of people falling into some 'illegal' category would then be instantly accessible.
Freedom is valuable because it has taken many generations to build, yet it can be demolished in the time it takes to fight a war or the single day necessary to hold an election. A state cannot be trusted to host independent records of people's DNA for their entire lifetimes, particularly if we cannot remember abuses against freedom that happened within living memory.