Having D used in production in a big company like Facebook is a big deal. No, it doesn't mean that D has taken over the programming world or anything like that, but it shows that the language is maturing and that real companies are now willing to use it in the real world - and it's a pretty major company at that.

So, this is just one step forward, but it's a big one and exciting to the folks who are fans of D - especially those who have put a lot of time and effort into it.