[anewaccountname]

So when I click reply to an email, and preserves your entire text at the bottom of my reply, I'm guilty of copyright infringement? How about when I forward the school newsletter to the person the school meant to send it to?

[mechanical_fish]

Not infringement -- I'm pretty sure that both these use cases fall under the "implied license" case mentioned in the link I provided, above. And it's important to note that there's a big difference between using someone else's copyrighted material and copyright infringement. Don't be fooled by (e.g.) the music industry's attempt to confuse these two concepts.

There's also a difference between copyright infringement and an infringing act for which you will be prosecuted, convicted, and fined. There is necessarily a lot of leeway in copyright law, precisely because everything written today now falls under someone's nigh-permanent copyright.

(It used to be that, in the USA, you had to affix a copyright notice to a work to secure the copyright. That changed in 1989 when the US ratified the Berne Convention. See http://en.wikipedia.org/wiki/Copyrights)