Germany's current account surpluses: Negative effect? How to solve them?
As requested in comments:

German banks lost a lot of money in the US sub-prime crisis and would have lost a lot more in Greece if the Eurosystem had not saved them. This is what might reasonably be expected if you run persistent trade surpluses: you gain foreign assets which may never be repaid or may be less valuable than you expected

The European Commission is supposed to investigate under its Macroeconomic Imbalance Procedure when a country's current account surplus exceeds 6% of GDP, and Germany's is now about 8%. In the end the Macroeconomic Imbalance Procedure might in theory become an Excessive Imbalance Procedure and potentially sanctions for euro-area member states of up to 0.1% of GDP. But it will not happen to Germany, for European political reasons. Wikipedia has a description and you can also read the latest Commission report 

In effect Germany is making stuff and sending it to foreigners without exchanging it for a similar value of imports. Eventually people in Germany might notice that they could have a higher standard of living which their mercantilist politicians and economists have been denying them

German savers and politicians are already protesting about low interest rates and perhaps one day might think that in a period of negative interest rates it could be sensible to consume (and import) more