Debt is bad (?)

This Debt as a percentage of GDP always intrigues me. Is having a high percentage bad? Check this out. Are the "top" countries badly managed (economically)? Are they in trouble (financially)? Click for an enlargement. Is Japan in big trouble? (I doubt it.) Is Italy in trouble? (Probably.) Is Greece in trouble? (Definitely!) Do these numbers mean anything? Maybe it depends upon who owns your debt, eh? China ($877B) and Japan ($768B) got lots of U.S. debt. I understand that much of Canada's debt is owned by pension funds, insurance companies, banks ... so it's owned by Canadians. How much does China and Japan have? I dunno.