Borrowed from: 

http://www.hyphenologist.co.uk/killfile/anti_troll_faq.htm

Subject: 5.7  LART (report to ISP)

Where a Troll breaks the rules of usenet or their ISP an
email or "LART" to abuse@ISP,name will often persuade the
ISP, newsserver operator, or their upstream providers to
cancel a users account.

Pro:
It often works.  It is traditional usenet practice.

Con:
Free ISPs are ten a penny, and the Troll can easily get
another account and continue as before.

Some Trolls can have several paid for internet accounts.

..... <Snip...snip...snip>

Visit the web page given above.
Ten a penny.
..