"Save the Date" cards: Are they necessary?

"Save the Date" cards were created to help the bride and groom notify their intended guests of their upcoming nuptials. "Isn't this redundant?" "Is the expense necessary?" are questions I initially posed to myself.
The answer is "It depends...". Many factors contribute to your decision. A wedding often has a lead time of a year or more, or you may be throwing a destination wedding, inviting a large number of guests from out-of-state, need to reserve large blocks of hotel rooms and want to let people plan in advance.
My experience has been no one has ever been sorry to have sent a "Save the Date" card. The cards served a valuable purpose...advance notice has allowed many of the cherished to guests to attend!