The Twitterstorm started when Daniel MacArthur, a geneticist at Harvard Medical School and the Broad Institute, tweeted that Wired's August cover story may have gone too far. The story suggested CRISPR would change the world, from making designer babies to species-specific bio-weapons. Chris Dwan, also from the Broad Institute, replied to MacArthur with a joke using the hashtag, and Twitter took it from there.
You may recognize CRISPR from when it set off a bioethical firestorm this spring after Chinese scientists published results claiming that they had edited the genome of human embryos. Though their experiments were not entirely successful, scientists called for a ban on using the technique on humans.