A cacher in my area puts his signature sticker on the cache containers he finds. On regular-sized containers, this practice always struck me as a little rude, but not necessarily harmful. The sticker, however, is quite colorful and was placed in one instance on a steathily-hidden, black film container micro. The cache was later plundered. I was surprised that an experienced cacher wouldn't understand what a bad idea it was to put a sticker there. I suppose future notes should instruct cachers to replace the cache in the same condition they found it, as well as location.