Gates and other truly wealthy people hire attorneys to protect their assets from the estate tax. There are a variety of legal tricks that make it possible to dodge the tax if you have the money to hire good lawyers. You'll notice wealthy families like the Kennedys and the Rockefellers don't worry about the estate tax. They know they don't have to pay it.

The estate tax falls most heavily on small business owners, farmers, and the like. A farmer can be land rich but dollar poor, meaning he has millions of dollars worth of farmland but little in the way of cash. That being the case, it becomes hard to protect the farm against the tax. The same applies to most small businesses. That's one of the major reasons why so few small businesses survive the death of the founder.

The estate tax is perhaps the ultimate form of government greed. Someone works hard all his life to build something, paying hefty taxes every step of the way. Then, if they happen to have built an estate above a certain threshold, the government can come in and take upward of 55% of it. The compliance costs of the estate tax mean the government doesn't actually collect that much every year in net taxes but it does mean a lot of families are denied the results of their efforts.

Interestingly, some of the strongest opponents of the estate tax are the National Black Chamber of Commerce and Robert Johnson, the man who founded Black Entertainment Television. He is probably the first black American billionaire. His argument is that this is the first generation of black Americans who've had the opportunity to build estates, so the tax denies them the opportunity to pass the efforts of their work on to their descendents.