Any number of excellent books have been written about project management and scheduling, but few of them confront this phenomenon head on, and I've now seen it at a bunch of companies. Someone important, or even just useful, can cause a lot of damage by having a bad memory. If they're a manager, it might become their employee's second job to stockpile email in case they need to "prove" who's mistaken at review time. If it's a peer, they don't pull their share of the work because they conveniently forgot to do most of it and someone else has to, or some schedule slips. This might be passive aggressive (if they're not a psychopath or an asshole), but since it's the holidays, let's consider that it might be a medical problem. Maybe they're eating badly?
A few suggestions for coping: Start ordering in veggie platters. Take them out for sushi whether they like it or not. Leave them Secret Santa Ginkgo Biloba supplements by their monitor. And finally here's a list of some nice articles from Psychology Today on food for your brain, which I rather enjoyed:chimp instead if your team mate or manager can't remember things after eating better.]