I consider a snippet its own artform, saying everything that needs to be said in no more than 300 words - a story with a a beginning, middle and end, only condensed. I would no more add a 301st word to one of my snippets than I would a fifteenth line to a sonnet or an 18th syllable to a haiku (supposing, of course, that I would ever actually write a sonnet or a haiku).
That's only me, of course. Other authors are free to bastardize their sonnets as much as they please.
