FAIR USE OF TRADEMARKS UNDER US LAW:
In the United States, trademark law includes a fair use defense, sometimes called "trademark fair use" to distinguish it from the better-known fair use doctrine in copyright. As with copyright law, the trademark fair use doctrine is premised in significant part on the First Amendment guarantees of free speech. Fair use is consistent with the more limited protection granted to trademarks, generally specific only to the particular product market and geographic area of the trademark owner.
Most trademarks are adapted from words or symbols already common to the culture, as Apple, Inc. is from apple, instead of being invented by the mark owner (such as Kodak). Courts have recognized that ownership in the mark cannot prevent others from using the word or symbol in these other senses, such as if the trademark is a descriptive word or common symbol such as a pine tree. This means that the less distinctive or original the trademark, the less able the trademark owner will be to control how it is used.
A nonowner may also use a trademark nominatively*—to refer to the actual trademarked product or its source. In addition to protecting product criticism and analysis, United States law actually encourages nominative usage by competitors in the form of comparative advertising
* NOTE:
Nominative use:
Nominative use, also "nominative fair use", is a legal doctrine that provides an affirmative defense to trademark infringement as enunciated by the United States Ninth Circuit, by which a person may use the trademark of another as a reference to describe the other product, or to compare it to their own. Nominative use may be considered to be either related to, or a type of "trademark fair use" (sometimes called "classic fair use" or "statutory fair use")
In C-USA's case, you can't even say that The Daddy is infringing on YOUR tradmark as he could be comparing his X500 with the real "Amiga" computer which you have absolutely bugger-all to do with.
