The communications network helped us all find out if friends and family were caught up in the London blasts, says technology commentator Bill Thompson.
It began, as these things so often do, with a phone call from an anxious parent.
More than 700 hundred people were injured in the blasts
My dad wanted to be reassured that I was okay, and was pleased to hear I was not in London where there were reports of a power surge on the Tube that had caused accidents and injuries.
And so I turned to the web, where the story was played out in a mixture of news reports, blog postings, photographs and stories.
Others have written about the importance of the blogosphere in providing testimony and eyewitness reports, of the fantastic effort going into keeping the Wikipedia page up to date during the day and how Flickr feeds and photoblogs provided a vastly widened eye for the public gaze.
Text and e-mail
But my concern was not the public sphere but the private one.
I sent text messages and e-mails to some, tried calling others, finding it impossible to get through to any mobiles, and fielded a dozen or so queries from friends who know that my schedule often takes me to London early in the morning, via Kings Cross and onto the Piccadilly line.
There was no bad news. Nobody called to tell me the worst; no e-mails arrived with someone else's name in the subject line.
And by the end of the day enough people were clearly okay and in a position to tell me if others had been affected for some sense of calm to return.
I checked the blogs of those I care for, relaxing if they had posted some comment, however trivial, about the events of the day.
Thanks to the network, websites, e-mails, chat, mobile phones, instant messenger, I was able to reach out to my friends and colleagues, able to reassure myself, and able to feel confident that if something had happened to someone close to me then I would have heard.
Immediacy of news
This also means, I am sure, that those who lost loved ones, friends or colleagues found out more quickly than they would have done if this atrocity had happened five years ago.
This will do nothing to diminish their pain.
I think that I would rather have known at once instead of having to wait hours or even days to hear, but I cannot be certain.
Many were left in a state of shock
Once information is moving faster, then it brings both good and bad news with equal speed.
It is a remarkable aspect of our networked society that we can reach out to those we know so easily and so effectively.
Once this privilege would have been reserved for the powerful, the wealthy and the famous. Now it is available to all of us.
I am writing this in the bar of the Cambridge Arts Picturehouse, waiting to go in to the UK premiere of The Last Mitterand, the opening film of this year's Film Festival. It feels good to be surrounded by people.
Thanks to the open wireless network I can also look at the BBC news website and see that the number of dead has risen to 37, and I grieve for every one of them.
But, more selfishly, I can reassure myself that no e-mails have arrived from friends and colleagues to tell me the bad news I do not want to hear.
And I will keep my phone switched on, silent, in the film tonight, just in case anyone calls or texts.
Bill Thompson is a regular commentator on the BBC World Service programme Go Digital