Indeed, but my point is more about the assumption that a URL to a public web page is shareable. I don't know that this is every explicitly mentioned in any of the RFSs, but it seems like an undeniable assumption given that the point is for it to be a resource locator. Technically one of these URLs with tracking and a MAC should still be shareable, I suppose, but the tracking would be useless. Webmasters could go even further and generate one-time-use URLs for every page load in every session. They would still technically be URLs, but similarly would be pretty clearly in opposition to the point of URLs.