As long as I've been online, I've seen discussions concerning copyright and crochet patterns. It tends to be a very confusing topic. As copyright is federal law and covers all kinds of things, defining it in terms that most can understand is difficult. An online search of "what is copyright?" led me to this: www.copyright.gov/circs/circ1.pdf
Basically, if you didn't write it, don't copy it for your friends or post it online. There is a very good article on why here: http://www.craftdesigns4you.com/stop.htm
There's nothing wrong with preserving your pattern books by photocopying the pattern you want to make so you can check off rows and circle sizes. That is considered personal use. Giving that photocopied pattern to a couple of friends, or worse yet, posting it online, is illegal. Instead, tell your friends, in person and online, where you found the pattern and where they can purchase it, or purchase it for them as a gift.
Ignorance of the law is no excuse, as any police officer will tell you. I like to believe that most crocheters are law abiding citizens - I say most as the whole Martha Steward thing comes to mind. Is sharing a pattern that someone else designed and wrote worth a criminal record?