On Monday May 16 Blottr , a citizen and collaborative journalism site, broke the story about a bomb alert in London.
As virtualeconomics.co.uk reported , the news was first tweeted early in the morning by one user who noted that the bomb squad was inspecting a suitcase  and some others who tweeted that the area around Trafalgar Square had been closed as the police was carrying out a controlled explosion around 9am.
A few minutes after 10am Blottr published the story adding pictures, detail and coverage of the events in the square.
Sky News first, and BBC next picked up the story only 3 hours later.
The story appears as the result of a powerful combination of citizen journalism and social media: Twitter first announced the news, then Blottr broke the story gathering, curating and publishing news, and then Twitter let it spread linking to Blottr's story.
"It was the only full story available of the incident for 3 hours, until Sky News put it as their "breaking" news, followed by the BBC. By this time, everyone discussing the story on Twitter (was) linking to our story, as the main source", Blottr founder Adam Baker told virtualeconomics.
In Wikipedia-style, everyone, via web or smartphones, can sign in and publish a story or make revision, edit and enhance texts, and add videos, photos and tags. "The power of Blottr derives from the fact you can break news as it happens, straight from your mobile device, no matter where you are", the site says. 
The person who originates the story is required to assign a location, category and title to it so it would be easier for users, searching by keyword and location, to find the story they are looking for.
What make Blottr stand out from other attempts of citizen journalism however is, as Tech Crunch reported , the "authentication algorithm: it attributes credibility to each story based on factors like how influential the author is on Blottr, how many other people have contributed to the story and how many times it's been shared on Facebook and Twitter or been bookmarked".
The idea of ranking credibility internal to the community is shared by another citizen journalism site, the image agency Citizenside, which uses a point-based game system  to give users points based on how many activities they do, how much they are engaged in the community and how trustworthy their contribution is.
"In any case, Blottr was first with an actual article that could be used to understand what was going on - it's not really journalism until you can read it to make sense of the situation, and Blottr's team did the heavy journalistic lifting of following up a lead, understanding what a number of disparate tweets meant, verifying the story, securing permissions on the only photo and turning the lot into comprehensible news", the article said .
Not everyone however is convinced that it was actually such a big news as it became.
A Shiny Shiny's post noted it had such a prominence because it was amplified by the London twittersphere.
"Essentially, there was a threat, a road was shut down and there was a controlled explosion. A similar thing happened on Tottenham Court Road (north london) a few months ago at lunch time, also with a controlled explosion. This is the sort of thing that happens in Belfast, relatively frequently, but the incidents would rarely make it to the national news", the article argued. "If it doesn't disrupt key Twitter people on their way to work, it doesn't get much coverage in the mainstream media", it added.
Was it a great example of how powerful citizen journalism and social media are then, or did it just have "undue prominence" due to the "London bias of Twitter users"?