Viewpoint: What dangers may lie ahead for libellous tweeters
On 2 November, Newsnight broadcast what are now known to be mistaken claims by former care home resident Steve Messham that he had been sexually abused by a prominent 1980s Conservative politician.
Following the broadcast, there was much speculation as to who that politician was. Some of this discussion was via Twitter, with individuals linking Lord McAlpine to the Newsnight report - causing his name to appear as a "trending topic".
Media reports suggest that Lord McAlpine may be considering suing at least some of those thousands of people for libel.
The legal position of an individual who posts content online, be it on Facebook, Twitter, or on comment sections of online news pages, is clear: He or she is responsible for that content. Ignorance of the law is not a defence.
When individuals post material online, they act as publishers and their publications are subject to the same laws as those of professional publishers, such as newspapers.
This includes publications made by way of a tweet. A retweet also amounts to a further publication.
The person who retweets that material will be responsible for the content of that retweet.
In addition, the individual who originally tweeted the defamatory tweet is also likely to be held responsible for any retweets.
While this may seem beyond the original tweeter's control, this is because it is a reasonably foreseeable consequence that a defamatory tweet might be retweeted.
It is not a defence for an individual to say that he was simply repeating a statement by someone else. Just because something is out there does not make it OK to repeat.
The courts consider each tweet to be a libel, and the more often it is repeated, the more damage it can do and the more libel actions it may provoke.
Furthermore, when it comes to proving the truth of the allegation, it is insufficient to point to the fact that somebody has been accurately quoted - the publisher has to prove the substance of the allegation.
In other words, if I were to make an allegation about my boss that is retweeted by my friend - my friend must be able to prove the allegation, not just simply that I had said it.
Even if you cannot prove that the tweet is true, there could be a credible public interest defence.
However, in previous cases the courts have made it very clear that they expect a defendant to demonstrate that he or she has engaged in responsible journalism before the defence will succeed, including verifying the story and giving the subject an opportunity to comment.
For people simply retweeting something they have read on Twitter, this defence is unlikely to succeed.
In these cases, people could be exposed to claims for damages approaching six figures depending on the extent of publication and any other mitigating factors - such as a swift public apology.
If Lord McAlpine does sue in relation to some of the recent tweets, the cases will join the increasing number resulting from individuals' use of social media.
In the UK's first libel case involving Twitter, New Zealand cricketer Chris Cairns was awarded £90,000 in damages after he was wrongly accused of match-fixing by Lalit Modi, the former chairman of the Indian Premier League.
In explaining his ruling, Lord Chief Justice Lord Judge said that as a consequence of modern technology and communication systems, stories had the capacity to "go viral" more widely and more quickly than ever before.
He said the scale of the problem is "immeasurably enhanced" by social networking sites.
The message we are hearing loud and clear from the courts is that the public cannot treat Twitter and Facebook as they would a casual chat in the pub.
Niri Shan and Lorna Caddy are media lawyers for London-based law firm Taylor Wessing. Niri can be followed on Twitter here. This article reflects the personal opinion of Mr Shan and Ms Caddy, and does not represent the views of the BBC.