That said, they don't provide any extra information about the questions with them, so it could probably be edited out without affecting the questions; after (I think) 24 hours, it won't be suggested as a tag. Then once we have moderators, it would probably be a good candidate for black-listing.
See also the SO blog post The Death of Meta Tags.
sci-fi as a tag could mean the subgenre of science-fiction known as sci-fi. From Wikipedia:
Forrest J Ackerman used the term sci-fi at UCLA in 1954. As science fiction entered popular culture, writers and fans active in the field came to associate the term with low-budget, low-tech "B-movies" and with low-quality pulp science fiction. By the 1970s, critics within the field such as Terry Carr and Damon Knight were using sci-fi to distinguish hack-work from serious science fiction, and around 1978, Susan Wood and others introduced the pronunciation "skiffy". Peter Nicholls writes that "SF" (or "sf") is "the preferred abbreviation within the community of sf writers and readers". David Langford's monthly fanzine Ansible includes a regular section "As Others See Us" which offers numerous examples of "sci-fi" being used in a pejorative sense by people outside the genre.
But a lot of visitors won't be aware of the distinction, so I think it's best to avoid it.