"Short Timer Syndrome" in newly resigned employees
It's been my experience that this afflicts most employees who resign and who are kept on until the last day. Most tend to work OK the first week of a two week notice, but the second is a disaster.
You have to ask yourself if it's worth keeping a lame duck around with the attendant impact on the morale of other employees around. The person is usually leaving for a reason that's not favorable at all to the organization, and the first question most employees ask the soon-to-be-departed one is "why are you leaving?". This spreads some discontent to be sure.
