The following pie graph provides an excellent visual on the size of the PIGS (Portugal, Ireland, Greece, Spain) debt in relation to the entire Eurozone.
Ireland (1.7%), Portugal (1.8%), and Greece (4%) are small potatoes and can easily be contained. However, if interest rates begin to rise in Spain (9%) and then move to Italy (23%), the contagion will be uncontrollable at that point.
This is the reason the European leaders are trying to put out the Irish fire as soon as possible. While they could care less about Ireland, they need to keep the flames away from these other countries.
The pie graph is on the left and the interest rate spreads are the right. The higher the rate, the more the market is pricing in default. (And the more it costs these countries to purchase additional debt)