DealBook, the New York Times blog, posts that General Electric has already sold off a baker's dozen of units, including the plastics unit where two of its former chief executives once worked. And it is in the process of selling its appliances business, one of its oldest units and the birthplace of a slew of everyday household items. But that apparently isn't enough for Stephen Tusa, a JPMorgan Chase analyst. Mr. Tusa downgraded the stock to "neutral" from "overweight," saying the company needs to sell off even more operations to restore investor confidence. And while DealBook doesn't note this, one unit that's already been the source of chatter as a possible sales prospect is NBC Universal.