I just need a few clarifications on Treachery. It destroys the coin being activated, unless that coin must be destroyed to use its ability.
So, bomb, goes off, Treachery is used, the bomb isn't destroyed, right?
Broadsides is used. Treachery is used. A second Treachery is used against the first. Does this mean that the broadsides gets through, and the first Treachery is not destroyed?
Treachery destroys the coin it is reacting to, period.
In a case like this, the the Bomb is destroyed by the Treachery. (The potentially confusing interaction here is that the Bomb is not destroyed due to its own ability, because its ability has been negated. Rather, the Bomb is destroyed by the Treachery, because "negate and destroy" is the Treachery's ability.)
In this case, the first Treachery is destroyed by the second, so the Broadside gets through.
Thanks for the questions!
If Treachery always destroys the coin being activated, why is there the mention in the rules of a Mate being used, Treachery used, and the Mate is not destroyed? Under the 'Negating Abilities' section.
Er, um... because part (b) of that example is totally in error. 
What I meant to communicate there is that the Mate does not sacrifice itself to destroy its target as it normally would, because its ability is wholly cancelled by the Treachery. However, what does happen is that the Treachery, as part of the Treachery's ability, destroys the mate.
Mea culpa and ten thousand apologies! I'll get this into the errata as soon as possible. Many thanks for helping find the error.
That makes sense. It seemed like a kinda wierd paragraph. Glad to help!
But the example above is totally legit if Mate was used to destroy a Captain's Monkey: Captain's Monkey negate it's destruction, so Mate isn't destroyed because the coin never worked.
Is it true?
I'm not sure I follow.
If a Mate attacks a Captain's Monkey and someone plays a Treachery to stop it, the Mate is destroyed and the Captain's Monkey survives, without the Monkey needing to use its ability, because the Treachery negates the Mate's attack and destroys the Mate.
Of course, if a Mate attacks a Captain's Monkey and no one plays a Treachery, the exact same outcome occurs, since the Mate is destroyed (this time, because of its own ability, which states that it must be sacrificed to make an attack) and the Captain's Monkey can use its ability to save itself.
Is that what you meant?
Yes, sorry... I made a mistake.
The Mate is destroyed due to his "activation", even if Captain's Monkeys save himself and negates his destruction.
I misunderstood the "negating ability" effect, as for rules: "...So if a negated coin's ability called for it to be destroyed in order to be used, the coin is not destroyed because the entire ability has been nullified. However, the original player's turn is still used up."
My only problem is on the rules of Treachery, Captain's Monkey and Mate.
So, my problem, was about this rules passage: "...if a negated coin's ability called for it to be destroyed in order to be used, the coin is not destroyed because the entire ability has been nullified."
If I destroy a Mate coin in order to destroy the Captain's Monkey, and Captains' Monkeys uses his ability to negate his destruction, is the Mate action nullified?
If so, is the Mate coin destroyed or not? (as per rules).
Do Captain's Monkey negate only his destruction (but the opponent's Mate coin action to destroy the Captain's Monkey is still used, so Mate is destroyed) or do Captain's Monkey nullifies the entire action? (as for Treachery, but without destroying the enemy-used-coin).
Treachery negates a full action, while Captain's Monkey only negates his destruction... but, in this case, the only action Mate took was to be destroyed in order to destroy Captain's Monkey.
So, the Captain's Monkey ability negated his destruction, and nullified the Mate coin's ability, who was the only action in play... so the entire action was nullified.
Last question... am I forced to use a coin's ability, or, can I choose to use it? (maybe, sometimes, I don't want to save my Captain's Monkey).
Thanks for your patience,
Alberto
Ah, I see! After thinking about this a lot, I think that you're right — since the Monkey's ability is to negate, and since negate is defined as causing a negated ability to not take effect, a Mate would survive an attack against a Monkey who saved itself, because the Mate's entire ability is nullified.
Very clever reading of the rules. I will add this to the FAQ.
Whether to use a coin's ability is always optional.
Thanks 
...
My compliments to You and to the game designers of Pieces of Eight.
It's really a great game! 
I'm not sure if I agree with your ruling on the Captain's Monkey and Mate interaction. It seems the Captain's Monkey only negates its own destruction. To me, this is different than negating an ability that destroyed it.
For example: If I have a Captain's Monkey in my fore and another coin in the crow's nest, and my opponent uses a Bomb to destroy them both, I would assume the Captain's Monkey can only use its ability to save itself. In other words, it only negates its own destruction. It does not negate the ability that causes its destruction, and therefore the coin in my crow's nest is still destroyed (along with my opponent's Bomb).
I don't know if I have that right, but that is how it seems to me.
To me, the Mate's ability is "destroy this coin to destroy any active coin of your choice." The Captain's Monkey only negates part of this ability, not the whole ability. It does not negate the part in which the Mate destroys itself. This seems different than Treachery that can negate a whole ability/action. Therefore, I think the Mate would still be destroyed if used against a Captain's Monkey that saved itself.
(I feel very presumptuous saying anything, because I know it is your game, I just wanted to share my opinion.)
Xibalba, you're right about the original intention of the Monkey's ability: It was that it would be able to prevent itself from being destroyed, but not really have any further interaction with any coin that attacked it. That's what feels right to me.
However, I think that a close reading of the way that it's written (i.e., using the specific word "negate," and considering the strict definition of what "negate" means in the rules) suggests the more recent and expensive ruling.
Maybe a better solution would be to re-word the monkey's ability to something like "...to prevent its destruction."
Because (for example), say that a Monkey was in front of a stack that was hit with a 3-Cannon "combination" attack. Under a "negate" ruling, the Monkey could stop all three coins' destruction. Under a "prevent" wording, however, the Monkey would live but the two coins behind him would be toast, which I think it more satisfying.
Anyone else have any commentary on this issue?
Yes, true.
I totally agree on this solution because, as you described below:
... so I prefer a Captain's Monkey ability who can prevent only its destruction (and only if active) than a negating ability (who is a strong ability, typical of the Treachery coin).
Cool. I think I'll make that change in the FAQ.
I think the actual wording is OK, since the Monkey "negates its destruction", not the action or coin abbility, as treachery.
True, but since the word "negate" specifically has such far-reaching rules applications, it's probably best to errata the wording of the Monkey's ability so as to avoid unnecessary confusion. I agree with Jeff that in order to make it clear how it is intended to work (which should be of utmost importance), the wording should be changed.