When do you tell?

[stu bollen <stu.jo@ibm.net>]

Need advice from the list. When I recently sold a bunch of parts, as
usual there was just one person who didn't pay up. After two weeks I
E-mailed him and the excuse was he didn't have my address. Another two
weeks and no response to another note from me. I know he's around
because he posted on the list recently. At what point should I warn
listers about dealing with this person? Collective wisdom appreciated
Stu