The problem is that not all land buyers/ owners are subject to the estate tax.  As the price of land moves higher and higher,  Land will not be moving into the hands of young guys wanting to start farming, but will become owned by the buyers of land not subject to the tax.    This is what has happened with nearly every manufacturing business started in the last 100 years.  

The new owners will be Corporations whose shareholders will be Pension funds, Insurance companies, "Non profit" organizations, Endowments, Venture capitalists, Hedge funds, Bershire Hathaways, and foreign investors.  Worst of all would be Sovereign Wealth funds from other countries that are buying shares up with all of their US dollars.

If you think farm management companies skim too much of the profit off for themselves now, Just wait until your kids have to work for an hourly wage from the China or Abu Dabi sovereign wealth fund.

The 10million+ dollar factorys, seed companys, and implement dealers have allready been handed over. 
The estate tax may seem fair to you, but it is the largest single thing most responsible for the gutting of America and until every organization is subject to a similar tax as individuals are or the tax is abolished, the wealth distribution will only get worse.