That requirement, however, went away in the 2001-2004 rules. You no longer have to win a protest to be exonerated. In the above example, the protest committee would hear the facts and (based on their judgement) exonerate you. They also could (and should) protest the first boat, make her a party to the protest, and possibly disqualify her.
On the flip-side, just because the other boat didn't protest doesn't mean you didn't break a rule. When I break a rule, I am honor-bound to take a penalty (or retire), whether or not the other boat protests.
Sorry to further derail the thread ... but I would like to pose a second possibility in this scenario. Suppose three spinnaker boats were sailing downwind at a common catamaran gybing angle (45 degrees or so) all three on starboard not overlapped but each one slightly inside of the other and about a boat length behind. The lead boat gybes onto port with no warning and the second boat crash gybes with the upper half of his crew dangling upside down in the water. The third boat had no room to gybe so headed up sharply resulting in a capsize (mast very nearly missed the second boat's hull). It is my understanding that the third boat can only protest the second boat and although the second boat took the only option available to him, would be found at fault UNLESS he protested the first boat.
I was the third boat and although I did protest the second boat, I realized that he didn't protest the first boat and I choose not to follow through in the room because I wouldn't be able to get to the person that started the calamity. The second boat and myself did have a lengthy friendly discussion afterwards though.
It is important to protest if you have been fouled.