They did on twitter last night, although granted not everyone uses twitter. I don't know if they did it in the official forum as well as any other means.
Yeah, I would be one of those non-twitterers. It can't be beyond the wit of man to have a message pop up in-game to warn people about downtime. Not everyone has bungie's twitter page or forums as one of their daily checked sites.
Also, not sure if this is just confirmation bias, but they always seem to do it during peak playing time for Europe.