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- The Writers Guild of America uses the ampersand to indicate a close collaboration with a writing (or other) partner--closer than a situation in which one writer is brought in to rewrite or fix the work of another. For those in the know, it is a convenient way to subtly indicate that one writer has not been brought in to rewrite of fix the work of another.
- Newspapers, journals and others choose to use it when they are citing sources. That's their style choice, not a grammar rule.
- In similar citings, academia asks that the word and be spelled out.
- Occasionally the term etc. is abbreviated to &c, though I can see no reason for confusing a reader with this. Etc. is already an abbreviation of et cetera and the ampersand version saves but one letter and isn't commonly recognized.
- Ampersands are sometimes used instead of andto distinguish the andwhen it is part of a name rather than the typical conjunction used when naming a series of items. Here, too, it feels like a stretch and more confusing than helpful. Wikipedia gives this example: "Rock, pop, rhythm & blues and hip hop." This also seems like an unnecessary affectation if we would but use the traditional serial comma like this: "Rock, pop, rhythm and blues, and hip hop."