France and Germany only have so much more they can borrow; if they run up their debtloads much more, their guarantees for Eurobonds would be worthless.
Europe just won't face facts.
Germany did contribute the EFSF, but how can it cover over 400 billion more? Italy has over 1.8 trillion of debt out. And France is close to a credit downgrade itself.
Here is the French Treasury site:
http://www.aft.gouv.fr/?lang=en
This was in 2010:

Last Bundesbank monthly report - start at page 24.
http://www.bundesbank.de/download/volkswirtschaft/monatsberichte/2011/201106mb_en.pdf