The Nonprofit Law Prof Blog: "Uncertainty about the estate tax has caused all sorts of problems for estate planners and their wealthy clients. The estate tax expired at the end of 2010, but if Congress does nothing, the tax in 2011 will affect more people than it did in 2009. And Congress may do something - but no one knows what Congress will do and whether it will be retroactive. In addition to all the other planning problems this causes, charities are beginning to worry about a possible effect on charitable giving."