All the major TV networks have broadcast continually since mid-morning, as soon as the gravity of the situation became apparent.

Initially, Channel Seven made the running when the drama began unfolding, literally, over the shoulders of presenters Kylie Gillies and Larry Emdur.

Emdur and Gillies covered the crisis for the next 40 minutes until they and their colleagues were evacuated from their building at 52 Martin Place.

Before they left, Seven journalists set up a camera pointing at the building opposite, from which they have derived much of their footage. They also established a newsroom in exile in another part of the city with coverage anchored from Melbourne.

Inevitably, the networks have at times struggled to fill air time with meaningful coverage. And equally predictably, that vacuum of information has often been filled with mis-information, fuelled by reports on social media.

Initial interest focused on the black flag the hostages were forced to hold at the window.

But assumptions that the flag represented Islamic State were soon scotched when it emerged it was in fact a Shahada flag. A little later, reports appeared that a man arrested in the vicinity of Martin Place was connected in some way to the siege only for NSW Police to deny that via Twitter.

Later reports that houses in Lakemba were being searched were also put to bed by the AFP on Twitter.

And, similarly, stories that the Harbour Bridge had been closed, that a no-fly zone had been established over Sydney and that there was an "incident" at the Opera House, proved wide of the mark as well.

TV networks and other news organisations have also had to negotiate a delicate tightrope between reporting one of the biggest breaking stories of the year and risking providing assistance to the hostage taker, who is quite possibly monitoring TV news and social media, or hampering the police operation.

Late this afternoon Seven reporter Chris Reason appeared to confirm on air that the network had been asked by police for tactical reasons to stop broadcasting live footage of the front of the café.

Broadcasters have also wrestled with the ethical issue of the sensibilities of the family and loved ones of the victims trapped in the Lindt café.

The networks have all chosen to obscure faces of the hostages where they have been visible through the window of the café, although late in the afternoon when a group of three, then a further two hostages escaped, no attempt was made to conceal their identities.