Date   : Thu, 15 Aug-1985 11:56:27 PDT
From   : Lauren Weinstein <vortex!lauren@RAND-UNIX.ARPA>
Subject: mail order and credit cards

Note that companies that take your credit card number down, even
for a purchase by check, may cause you some problems.  In particular,
these companies often "run" your number (for verification) for the 
amount of the purchase through the credit card authorization computer,
which eats down your available credit even though no actual purchase on 
the credit card is being made.  While the lack of a followup purchase
will normally eventually timeout the resulting "purchase authorization"
after some period of time (typically two weeks or so) that is credit
that is unavailable to you during that time--important if you have low
credit limits.  Also, the credit card firms may become irate about
this practice if it occurs too often.

--Lauren--