One aspect of this would be future possibilities of targeting viruses, poisons et cetera to a specific genome. But such targeted bioweapons seem more likely to be broadly targeted to ethnic groups. See e.g. here. A more general answer would be that by making your genome publicly available you also share all inferences that can be made form your genome with anyone who wants to make them. The set of inferences that can create risks for you do not only include the ones that are accurate and scientifically robust, but also all such inferences that gain some credibility in a society—which means that you are at risk, generally, to become a target based on real or fictional properties of your genome.