Far too many people make the estate planning mistake of relying on verbal or written promises that contradict the will or trust.

FORBES: Estate of Richard Pratt, Australian Billionaire, Defeats Mistress In Court

Now, if the Telegraph is correct, the Eurozone as a whole is planning to repeat the mistake, and become just like Greece.

FORBES: Eurozone Leaders: Now They're Making the Crisis Worse Through Stupidity

Lazetta Rainey Braxton says grandparents can make the mistake of not planning to cover the expenses of catastrophic events, such as significant medical and long-term care costs.

WSJ: Grandparents Helping More with Family Expenses