Social networks are now becoming support networks. Others shared their stories: "My house burn down last year because of a forest fire … I sort of know what you're going through (the zombie-ness, the all over emotion, etc etc)." A few even urged her to post her PayPal account details so they could send her donations, under the initial post: "Who's down to get a collection started for [her] and [her] family?" The stream of support so overwhelmed her and her brother, Colby, who had helped the pilot of the US Navy F/A-18 Hornet fighter jet, that they later posted a YouTube video to say thank you.

The smouldering ruins of a fighter jet that crashed into Devin Smith's building. Thomas Tudehope, a freelance social media consultant, said this was a perfect example of how social networks could connect people across continents, demographics and cultures to rally behind a stranger. "Traditionally if you wanted to help someone there was always another component to it but social media removes that," he said. "If something goes viral it elicits a reaction, a different sense of connection to the issue. When it comes to your front door it's easier to help because you didn't have to hunt down for it." He was unsurprised by the level of generosity exhibited on Ms Smith's Reddit thread.

"During the London riots, people banded together and formed the 'Broom Army' to clean up the streets. Social media facilitates communities working together for the greater good." This week, a single tweet foiled a carjacking attempt in Johannesburg, South Africa, and saved the driver who was shoved inside the boot. The man messaged his girlfriend who turned to Twitter, rather than to the police, for help. "Be on the look for DSS041GP my boyfriend has just been hijacked and is in the boot please RT." A retweet got the attention of @Pigspotter, a Twitter handle that sends roadblock notifications in Johannesburg. It began tweeting the situation in real time to more than 110,000 followers, many of whom were from private security forces.

Emergency service workers and law-enforcement teams joined to track the mobile device and chase the vehicle. About two hours later, the carjackers drove into a roadblock and abandoned the car. The armed bandits escaped on foot, and the man in the boot was rescued. "It's a beautiful network where, when we have a genuine emergency, all the guys just get up and go, working together. Nobody expects anything in return. Last night, thank God, was a success," a security service company co-founder later tweeted. Howard Errey, a psychologist and social media expert, said Twitter unwittingly created a social model that encouraged civil behaviour and altruism. "There is the potential for your tweet to spread far and wide through unknown networks – so good news or altruism has a pay-off of spreading your network or influence or reputation and building followers," he said. "For those giving a commercial donation, as well as for the good feeling, the potential secondary pay-off in terms of promotion could be huge."

Perhaps that explains how Lauren Lane and Daniel Welch from Somerset, England, used Twitter to garner $15,000 worth of freebies and save their wedding. At the end of last year, they lost a $7000 deposit when the event-planning company organising their wedding collapsed six weeks before they were to marry. Mrs Lane's Twitter appeal, with the help of her bridesmaids, sparked offers of jewellery, clothes, a three-tiered chocolate cake, a magician, a make-up artist, a photographer and a wedding planner - all for free or at a discounted price. "It was a lovely wedding and I cannot believe how many people and businesses came forward to help us – it was amazing. I had gone on Twitter on the off-chance that someone might be able to help us but it just went mad," Mrs Lane told The Guardian. Mr Errey says: "We are enormously hungry to simply connect with others and ... even though it doesn't make obvious sense to help someone, we do it anyway."

He said help and support services had a lot to gain in the use of social media and not-for-profit organisations such as World Vision had done it particularly well. "Some support services are reluctant to go online because they see that their value is only visible in a face-to-face context," he said. "However, in certain online contexts they can be helped to realise greater reach and spread their value more widely and rapidly."