I have a form where users can make a booking on behalf of themselves or others. First is a choice column where you specify if the booking is for you or someone else. Second is a person or group field, which has current user as default value, but I'd like to remove the default value if the user specifies that they're making the booking for someone else. That way they don't have to delete their own name (not difficult, but the easier the better).
As a minor work around I have a rule which disables the person or group field unless you're booking for another person.