I formerly worked for a large publisher of loose-leaf analytical material.
Intellectual property, and specifically copyright, was our bread and butter.
 
While I am also not a lawyer, I believe Aaron is essentially correct.  The
fair use exemption is of particular interest to libraries, who were major
customers of ours.  Specifically, the photocopy machines in libraries are
always in view of staff, to prevent abuse of the copyrights.  No one minds
copying a few pages, but there is a point where "theft" of copyright
material becomes a problem.
 
To be safe and courteous, one should always request permission and provide
attribution when directly quoting material.  Legally, I believe permission
is not expected or required if attribution is made and the amount of
material quoted is not significant relative to the original material.  For
example, of one were to quote and attribute a few paragraphs from a 500 word
(more or less 4 pages) article, this would probably be considered as "fair
use".
 
Lloyd