The real fashion police...
It would be a good way for historical archaeologists to date excavation levels in landfill sites. A hundred years from now, a team of researchers are excavating a landfill, and all of a sudden, they start turning up bell-bottom trousers and tie-dyed tee-shirts, they'll know they've reached the 1970s. A little further down, and they start turning up women's girdles, with the garter clasps, and they know they've hit the 1960s. Mickey Mouse hats and coonskin caps, the 1950s, and so on. The same goes for consumer fads, like transistor radios, and hula hoops.