Researchers at TGen have developed a technique to identify trace amounts of an individual's DNA in a mixture of, for example, blood. While this is good news for forensic investigators, it is not so good for public data release. The human genome reference, the major product of the Human Genome Project, is a mixture of several individual's DNA. This was done so that no individual genome could be discerned from the freely available human reference. That may no longer be true and it has NIH rethinking its public release policy. That said, most human sequencing done now is not mixtures of DNA, but DNA from single individuals and the resulting sequence data must reside in a protected access database anyway to allay privacy concerns.

You can read the original paper in PLoS Genetics (an open access journal): Resolving Individuals Contributing Trace Amounts of DNA to Highly Complex Mixtures Using High-Density SNP Genotyping Microarrays.