I do not plan to add user id tracking until there is a specific need. (That specific need would be probably some sort of user cohorts and we can see at that time whether there is a more privacy-sensitive way of doing that.) For now, just a random token will do fine. Since UploadWizard is a single-page application (we do not need to track users across page loads, at least for a funnel analysis), we don't even need to put it into local storage.