In a world where every companies are so focused on trademarks and profit, Jack Daniels is a breath of fresh air. Their signature look and design is ripe for imitation, but you won't have to worry about the lawyers pouncing on you.
Protecting your brands is only right. You've created something from scratch and built it up enough that someone else wants to imitate it. This can be a problem when a design evokes thoughts of your brand, but it's for some other person's message. Luckily, the Jack Daniels brand has found a way to handle this politely and professionally.
When a new book by Patrick Wensink borrowed the Jack Daniels design for the cover, the lawyers sent a kind letter, appreciating his love for the brand but politely asking to change the cover the next time it is reprinted. He also had the option to change it sooner, to the greater appreciation of Jack Daniels, and they'd be more than happy to help out with the cost.
This is an effective way to both protect your brand's image and gain even more appreciation from a fan—and possibly making new fans with such a simple act of kindness.