When you lend money you assume a risk of default from the other party. Thats basic economics. There is no gain without risk. So greedy people that loaded on junk grade bonds from Greece and now are suffering the consequences, should have predicted this.
The way I see it, you've got an alcoholic (Greece), and a bartender (Germany) who should know better but kept giving him drinks. The alcoholic bears full responsibility for their actions, but a pox on the bartender as well for aiding and abetting the acoholic's dysfunctional behavior.
In my mind it's downright immoral for people to be buying the government debt of heavily indebted countries like Japan, Greece, USA, Italy, Spain, etc. All you are doing is helping them sell their own children (literally!) into debt slavery.