Is the embargo dead as a tool to manage the news?

The big news of the day, that David Miliband is not going to put his name forward to be considered for Labour's shadow cabinet, was released on embargo a few moments ago at 5pm. Mr Miliband also conducted a number of one on one interviews with the political editors of the broadcasters this afternoon. All solid tools of media management used by politicians and indeed businesses for many years.

One problem is that I, and many other people, have been well aware of this news for nearly an hour before the mainstream media broke the news. Releasing news via an embargo used to ensure that a narrative could be shaped before the news actually became public knowledge. No more. With so many people now using social media as their primary source of news the embargo must surely be on its last legs.