Recently the DigiNotar CA was hacked, and rogue certificates were issued. Since they also issue certificates on behalf of the Dutch government, the government made a statement about it as well, basically claiming: 'don't visit the website if you get a security warning from your browser'. Good advice in itself, and better than DigiNotar itself which claims 'ignoring that warning is 99.9% safe', but it ignores browsers with CA trust stores which have not been updated yet.
Assuming a non-updated browser (trust store), isn't a user vulnerable for Man-In-The-Middle attacks on any website, not just the ones which had a valid DigiNotar certificate? I know you can check the certificate chain on a website, but I never do, and I know for sure my parents never do.
Is SSL-trust really only as strong as the weakest CA, and is there a way to fix that?
Update 2011-09-06: An independent report by Fox-IT on the DigiNotar hack was made public