Almost all things are copyrighted the moment they are written, and no copyright notice is required.
Copyright is still violated whether you charged money or not, only damages are affected by that.
Postings to the net are not granted to the public domain, and don't grant you any permission to do further copying except perhaps the sort of copying the poster might have expected in the ordinary flow of the net.
Fair use is a complex doctrine meant to allow certain valuable social purposes. Ask yourself why you are republishing what you are posting and why you couldn't have just rewritten it in your own words.
Copyright is not lost because you don't defend it; that's a concept from trademark law. The ownership of names is also from trademark law, so don't say somebody has a name copyrighted.
Fan fiction and other work derived from copyrighted works is a copyright violation.
Copyright law is mostly civil law where the special rights of criminal defendants you hear so much about don't apply. Watch out, however, as new laws are moving copyright violation into the criminal realm.
Don't rationalize that you are helping the copyright holder; often it's not that hard to ask permission.
Posting E-mail is technically a violation, but revealing facts from E-mail you got isn't, and for almost all typical E-mail, nobody could wring any damages from you for posting it. The law doesn't do much to protect works with no commercial value.
References
"You get copyright protection automatically - you don't have to apply or pay a fee. There isn't a register of copyright works in the UK."
"Copyright prevents people from: distributing copies of [your work], whether free of charge or for sale"
Copyright protects your work and stops others from using it without your permission.
You get copyright protection automatically - you don't have to apply or pay a fee. There isn't a register of copyright works in the UK.
You automatically get copyright protection when you create:
original literary, dramatic, musical and artistic work, including illustration and photography
original non-literary written work, such as software, web content and databases
sound and music recordings
film and television recordings
broadcasts
the layout of published editions of written, dramatic and musical works
distributing copies of it, whether free of charge or for sale
renting or lending copies of your work
performing, showing or playing your work in public
making an adaptation of your work
putting it on the internet
Copyright overseas
Your work could be protected by copyright in other countries through international agreements, for example the Berne Convention.
In most countries copyright lasts a minimum of life plus 50 years for most types of written, dramatic and artistic works, and at least 25 years for photographs. It can be different for other types of work.
"Copyright is a form of protection provided by the laws of the United States (title 17, U.S. Code) to the authors of "original works of authorship" including literary, dramatic, musical, artistic, and certain other intellectual works. This protection is available to both published and unpublished works. Section 106 of the 1976 Copyright Act generally gives the owner of copyright the exclusive right to do and to authorize others to do the following:
To reproduce the copyrighted work in copies or phonorecords; To prepare derivative works based upon the copyrighted work; To distribute copies or phonorecords of the copyrighted work to the public by sale or other transfer of ownership, or by rental, lease, or lending; To perform the copyrighted work publicly, in the case of literary, musical, dramatic, and choreographic works, pantomimes, and motion pictures and other audiovisual works; To display the copyrighted work publicly, in the case of literary, musical, dramatic, and choreographic works, pantomimes, and pictorial, graphic, or sculptural works, including the individual images of a motion picture or other audiovisual work; and In the case of sound recordings, to perform the work publicly by means of a digital audio transmission.
In addition, certain authors of works of visual art have the rights of attribution and integrity as described in section 106A of the 1976 Copyright Act. For further information, request Circular 40, "Copyright Registration for Works of the Visual Arts."
It is illegal for anyone to violate any of the rights provided by the copyright code to the owner of copyright. These rights, however, are not unlimited in scope. Sections 107 through 120 of the 1976 Copyright Act establish limitations on these rights. In some cases, these limitations are specified exemptions from copyright liability. One major limitation is the doctrine of "fair use," which is given a statutory basis in section 107 of the 1976 Copyright Act. In other instances, the limitation takes the form of a "compulsory license" under which certain limited uses of copyrighted works are permitted upon payment of specified royalties and compliance with statutory conditions. For further information about the limitations of any of these rights, consult the copyright code or write to the Copyright Office.
WHO CAN CLAIM COPYRIGHT
Copyright protection subsists from the time the work is created in fixed form. The copyright in the work of authorship immediately becomes the property of the author who created the work. Only the author or those deriving their rights through the author can rightfully claim copyright."