Last summer, my son started a collection, which he keeps in a shoebox in our garage. It began innocently enough, as he collected rocks from the "moon", pinecones, and sticks. I loved it. It was so cute to see his fascination with ordinary objects, and brought me back to my own childhood (I had forgotten how valuable parking lot gravel can be). His collection was something I felt I could give him complete ownership over.
And then, things took a strange turn. My son began collecting garbage. Used lollipop sticks, candy wrappers, chewed gum, paper plates, empty milk boxes, an old pair of shoes, a sock with a hole in it... Things that I had thrown away in the kitchen, would mysteriously appear in his collection. In order to keep the bugs at bay, my husband and I have had to start regulating his collection. Being a sentimental person myself, I have been a little reluctant to completely hijack his choice of treasures, but, as my husband put it, "Sometimes trash is just trash."
And that's an important lesson to learn too.