Limitations of genetic ancestry testing

From the EurekAlert release about an upcoming Science article:

Some of the tests’ limitations identified by Bolnick and her co-authors include:

• Most tests trace only a few of your ancestors and a small portion of your DNA,
  
• Tests are unlikely to identify all of the groups or locations around the world where a test-taker’s relatives are found,
  
• Tests may report false negatives or false positives,
  
• Limited sample databases mean test results are subject to misinterpretation,
  
• There is no clear connection between DNA and racial/ethnic identity,
  
• Tests cannot determine exactly where ancestors lived or what ethnic identity they held.