Publishing a form — What can't be asked publicly

Under the palette, a collapsed line tells you how many fields can never appear on the form; open it and each one is named with the reason why. Relation is out because a public picker would broadcast the linked table's record names to the internet; Lookup and Rollup are calculated from linked records; Auto number assigns itself on submit; People means nothing to someone outside the workspace. Everything else is fair game — text, long text, numbers, currency, percent, rating, progress, dates, yes/no, choices, email, URL, phone, address and file uploads.