Reading your reply, Aug 30, to the ocean-scientist....
I take it that you can draw the line (for a person keeping an "unlisted
number") at whether someone will take the time to type out a subscribe-me
command, joining temporarily?
Am looking for a wall more solid than that. Data entry workers can be
hired to go through, copying lists two or three a minute - if they get the
knack, making up commercial/mailing (post office junk) lists. For
example. We want to put dampers on the quick-scan business, I think.
Another 2 cents.