This is a very good object lesson in "Don't hang your brand on Facebook" (or any other service that you don't control or have an SLA with). Eclipse existed long before the Twilight series, and here it is ousted because it has less mass appeal than a movie about horny vampires. Obviously seniority and first-to-field isn't a factor with Facebook.
It really sucks for the Eclipse project, though. I hope they're able to get it back, though knowing Facebook, I'd be genuinely surprised if they did.