Bundesbank exposure to the Target2 imbalances
A summary is that the Bundesbank is liable for only 27% of ECB losses on Target2. While it presently has reserves of €129 Billion before calls on German taxpayers will become necessary, loss provisions already made adversely affect German taxpayers with an increase from €4.1Billion to €7.7 Billion. The legal position is unclear should a country such as Greece leave the EMU as is the situation of a complete euro break up.
UPDATE A link with much more background on the TARGET2 debate has been provided in a comment it is here.