All government debt throughout the world is ‘unsecured’ - what is the ‘full faith and credit’ of a sovereign government that can not pay it's debt? What, then, is the debt of that sovereign worth to an investor?
When that happens, the government bonds already issued and held by investors begin to fall in current cash value (what it can be sold for today versus the originally paid issue price) and that government finds itself having to pay interest rates on newly issued 10 year bonds that make your 29.99% credit card look like free money.
Take a look at the Greek, Portugese, Spanish and Italian 10 year bond rates - the higher the interest, the more trouble the country is in.
Conversely, the United States and German 10 year bonds are trading at or near all time record low interest rates. For now.
Further explanation of the reasons for the US 10 year being where it is can be found in a post I made on September 11, 2011 -
http://www.freerepublic.com/focus/f-chat/2776797/posts
So far, I've seen nothing since that post to cause me to change anything in it.
The Greeks are not thieves, but their sovereign government is bankrupt.
“Our US debt regime is not dependent on little, kleptocratic debt regimes of southern Europe”, but it is dependent on the world's largest financial institutions, and we are going to loose some, part, or all of them before this is over.
:)