"Not collecting treasures prevents stealing."
If you learn one thing from Tao Te Ching, it's the art of preemption. Rather than focusing on the back end, trying to rein in a problem after it's spiraled out of control, TTC emphasizes the ease with which control and power are exerted when a situation is just beginning. In this case, the idea is expressed in terms of treasure and stealing. Instead of investing in security and insurance and weapons to protect your treasures (and stressing out about the never-ending prospect that you're going to lose them), prevent the whole situation before it even becomes a situation and don't collect the treasures in the first place.
Going deeper, this statement also encourages us to think about the total effect of our actions on other people. By collecting treasures, you are going to inspire envy and greed in other people and potentially inspire one of those people to steal from you. I know it's normal to put all the blame on the thief in this case, but if you have the intelligence to see how your decisions affect other people, then you already bear some portion of responsibility for the effects of your decisions. You'd might as well embrace that fact and think of all your actions as potential influences on others, influences that will shape your life for better or worse--you decide.