Quotes from the article:
The U.S. government is surreptitiously collecting the DNA of world leaders, and is reportedly protecting that of Barack Obama. Decoded, these genetic blueprints could provide compromising information. In the not-too-distant future, they may provide something more as well—the basis for the creation of personalized bioweapons that could take down a president and leave no trace.
Personalized bioweapons are a subtler and less catastrophic threat than accidental plagues or WMDs. Yet they will likely be unleashed much more readily.
5 page article.....: http://www.theatlantic.com/magazine/archive/2012/11/hacking-the-presidents-dna/309147/