Spain, Portugal and Ireland are also vulnerable. In theory, the EU won't let member states default, but as Yogi noticed, practice doesn't always follow theory.
http://www.marketwatch.com/story/debt-disaster-fears-rumble-from-athens-to-london-2009-12-16By Polya Lesova, MarketWatch
FRANKFURT (MarketWatch) -- Rumors of a debt disaster are swirling around Europe, from Athens to Madrid and all the way to London.
Investors have rushed to sell Greek bonds since the newly elected government of George Papandreou made a startling revelation: the deficit will soar to over 12% of gross domestic product this year, well above previous official projections.
Greece's predicament has escalated concerns about contagion in other European countries whose finances are in poor shape. Just this month, the ratings of Greece have been cut both by Fitch Ratings, and, late Wednesday, by Standard & Poor's, and major agencies have warned Spain and Portugal of possible cuts.The market reaction has been swift, and brutal. The euro has dropped below the key $1.50 level. Credit-default swaps on Greek government debt -- essentially, bets that Greece will default -- have ballooned.
The ASE Composite stock-market index /quotes/comstock/! (XX:??? 2,119, -49.83, -2.30%) has dropped more than 20% since mid-October, dragged by shares of lenders including Piraeus Bank, EFG Eurobank Ergasias and National Bank of Greece /quotes/comstock/13*!nbg/quotes/nls/nbg (NBG 5.22, +0.35, +7.08%) . (more)