It looks like Barracuda has taken a new and interesting direction in the enterprise fight against spam, although I'm not so sure that this is such a good thing.  By integrating an Outlook plug-in that can train the Bayesian filter of their spam firewall appliance product, they have given the user more power to decide what is spam and what is not.

Barracuda Networks, the leading provider of enterprise-class spam firewall solutions, today announced the immediate availability of a Microsoft Outlook plug-in that will seamlessly integrate with the Barracuda Spam Firewall 300, 400 and 600 models.

While the announcement does not go into detail as to whether an individual users decision to flag a message as spam applies to all users, I would suspect this to be the case.  For anyone who is interested in implementing such functionality, just recognize that should not be the first and only line of defense for your organization.  

It's clear that once a spam gets to a users desktop, its risk to your organization rises dramatically.  In my opinion, the best policy is "Keep it simple…."  Overall, you're not saving any money by passing this responsibility off to your users and what's worse, once it gets to the user, it's most likely already too late.  Stop it before it gets anywhere near the desktop is always going to be your best policy, this type of solution has the potential to breed laziness on the part of the administrators who should always be on their toes.