Panopticlick shows if you can be uniquely identified, but it doesn't show if you have been uniquely identified. I'd find it useful for the site to show me a record of my past visits ("You last visited the site on...") as a proof of concept, but the EFF may be intentionally avoiding any privacy issues. This is important, as uniqueness isn't in itself a bad thing, if your unique identifiers change on every page load. For example, it would be enough for a user agent switcher plugin to append a random number for every page load to make you look like a first-time visitor every time.