it's harder to lose your mug if you can clip it onto the side of your backpack.

These are so awesome, especially for Burning Man. First, you need to have a cup EVERYWHERE you go, otherwise you won't get to enjoy all of the wonderfully free drinks and coffee. I recommend having a cup with a lid on it when you go out on journeys, but for my morning coffee run to Zombies camp I would have loved one of these. They are lightweight and clip on to your backpack, pants, shirts, or even bike for easy transport. And coffee is just so much more enjoyable when it's in a real mug.

These are also great if you bike ride to work because you can just clip it onto your bag and stop into the coffee shop for a break without using one of those wasteful cups!