Voidable contract example

In contracts, voidable is a term typically used with respect to a contract that is valid and binding unless avoided or declared void by a party to the contract who is legitimately exercising a power to avoid the contractual obligations.

A contract may be voidable on the grounds of:

Fraud
Mistake
Misrepresentation
Lack of capacity
Duress
Undue Influence
Abuse of a fiduciary relationship
For this week's discussion board address the following:

Should we allow for voidable contracts? Why or why not?
From the list above, provide an example scenario for one (not all) of the listed grounds. For example: Duress: Max tells Rhonda that he will kidnap Rhonda's children if she does not enter into the contract. Rhonda signs it, but later wants to get out of it. This will be a voidable contract based on duress.
From the list above, add another reason that you think should be ground to make a contract voidable and explain why it would be a good addition.
Part Two:

CONTRACT ISSUES AND WORKSHEET

Before you start on this week's part of the project, you learn more facts about the negotiation of this contract:

Bob decides that he wants the toys and calls you to set up a meeting to discuss the price and to examine the collection of toys to make sure they are in excellent shape.

On October 4th, you meet at a local restaurant whereupon Bob examines the toys, which are up to his standards. You offer to sell them to him for $750.00. Bob scoffs and offers $650.00. Although you are a bit frustrated with his counteroffer, you remember that you really need the money so you offer $725.00. Bob grumbles and increases his offer by a mere $10 to $660.00. He claims he will not pay a penny more. You lower your price to $720.00 and inform him that this is your best, final offer.

Bob states that he will not pay that price and departs the restaurant. Feeling defeated you collect your toys and go home. As you walk home, you wonder if you should have continued the negotiation and gone lower seeing that $700 is your goal price.