Why Is Science Fiction So Fascinated By Black Goo?

Today's Comment of the Day comes from hamnotono who, fresh off the news that Helix has been renewed for a second season, asks what the deal is with science fiction's fascination with black goo?

When did "black goo" become the default sci-fi mystery substance? X-Files, Prometheus, Helix, probably others I'm forgetting. Give me some bright orange crazy goo! Teal! Grey! There's so many other options!

So, what's the deal with this science fiction trope, folks? Point out some of your favorite on-screen examples or just nominate an on-screen successor. Commenter CarrerCrytharis suggested green slime (Ghostbusters, Ninja Turtles) could be up next, while commenter Dr. Emilio Lizardo went with Star Trek's take on red matter.