I know I am late to this game, but as someone who makes a living helping people reduce/avoid estate taxes, here are a few thoughts:
First is a correction - for 2013 the Federal estate tax is a flat tax of 40% (not 55%) on the excess over $5,250,000. The 20% going to the wife is not taxed (Until she dies assuming she has more than $5 million). Assuming the trust for his son with the $7,000,000 life insurance policy was set up correctly, it will not be subject to estate tax.
Estate planning can be very simple, or very complex, depending on the primary goals. Bill Gates and Buffet's planning is most likely very simple -- I give what I can tax free to (fill in the blank), with the remainder to charity. However, when someone's goals and desires do not line up with charitable planning, it can get much more complex. There are almost endless ways to reduce estate taxes, but they all come with a price (some are very expensive to set up and maintain, others result is a loss of access or control). As with most all things in life, we balance the good and the bad and make the best choice we can.
Rfenst is correct. When you look at the historical legislative history for the estate tax, the purpose of the tax is an effort to prevent the creation of an American royal class.
At the end of the day, the 99% of us do not really need to worry about estate taxes (although there are a lot of other reasons to do estate planning other than taxes) -- for a married couple they can easily exclude from the Federal estate tax over Ten Million dollars.