Could be a very interesting day on Monday. If S&P has downgraded the US to AA+, they are now going to need to be consistent about the rest of Europe. Lookout PIIGS...and France too....
A fair few pension funds are invested in AAA only bond funds, although the trend in Ireland (and probably other non-US countries) is to invest purely in Eurozone bonds because of the currency risk. There is going to be carnage in the Treasuries market on Monday, just carnage. And if France goes, it'll be carnage over here too.
Same happened to Greece last summer - they got downgraded and fell out of the Merrill Lynch series of bond indices (which are commonly used) and pension funds had to get rid on the spot. So yields kept shooting up. The cleverer investment managers kept the Greeks in a separate subportfolio (with Trustee consent obviously) on behalf of the pension scheme rather than selling off just cause their mandate said they had to and waited for a better exit point which happened a few weeks later.