You might want to read this:

http://www.of-counsel.com/of-counsel/News/Etiquet/Etiquet.htm

...marks the sender as a "twit," who other users can filter out with the "twit filter" in their software.

or look up twit filter here:

http://www.ibiblio.org/j126/Internet/MainPage.swf

(that goes back to 1996)

or see 'ignore list' here:

http://objectmix.com/faq.php?faq=vb3_board_usage#faq_vb3_troublesome_users


or here search for 'twit filter' on the page:

http://www.professional.org/newuser.html