Ireland went bust because it couldn't afford to bail out its banks. They were too big to save.
So it's interesting to see this list of the size of banking systems in other European countries (measured by assets), relative to each country's overall economy (annual GDP).
Yes, Ireland is something of an outlier -- its banking system is nearly 9 times as big as its economy.
But in all the big economies of Europe, bank assets dwarf annual GDP -- the ratio is more than 2:1 in Germany and Spain, and more than 3:1 in France and the UK.
Bank assets as a percentage of GDP
United Kingdom 389
(For comparison, total banking assets in the U.S. are equal to approximately 82 percent of GDP.)
List from the Atlantic's Megan McArdle, via Marginal Revolution