Unlike the contents of your inbox, bank statement, or Facebook timeline, your DNA quite literally defines you. It's strange, then, that in an age where sequencing the genome is becoming trivial, we don't give a second thought about the privacy issues surrounding the chemicals that make us who we are.
In fact, most states in the US have absolutely no laws whatsoever to govern surreptitious genetic testing. If that surprises you, it gets worse. Back in 2006, the particularly forward-thinking state of Minnesota passed a law demanding that written consent had to be obtained for collection, storage, use, and sharing of genetic information. In 2011, however, the Minnesota Supreme Court judged that the state's own department of health was in violation of that very law.
Most universities and funding bodies already have strict ethical standards in place for dealing with DNA samples. In fact, it's pretty much the norm to anonymize data as soon as it's collected, so that scientists are never able to tie samples to an individual. Instead, they're only ever referred to by a number.
Before 2001 DNA was only collected when a person was charged with an offence and was destroyed if the person was acquitted. This changed in 2001 to allow DNA to be kept indefinitely. In 2003 the law was changed again to allow DNA to be taken on arrest for a recordable offence (rather than at the point of charge).
Recordable offences are include all offences that could lead to at least one year’s imprisonment as well as such other minor offences as begging and being drunk in a public place.
Looking at the "DNA Database Timeline", it appears that the 2010 switch of DNA retention to the Scottish model has yet to be accomplished so it appears that DNA of those arrested but not convicted is retained for periods of 6 and 12 years.