Last month, Facebook celebrated its 10th birthday. The customised 10 year anniversary videos shared by many Facebook users, reflecting their (largely positive) experiences since joining the site, paint a rosy picture of the company's first decade.

Indeed the social media networking site has much to be credited for: it has facilitated global interaction at no financial expense to its ordinary day-to-day users; provided a platform for debate; and enabled the promotion of social and political causes on a much larger scale than would have been possible previously (think Kony 2012).

But such a novel and ambitious concept was bound to encounter some difficulties, many of which have been legal in nature. There are, for instance, ongoing privacy actions in the US against Facebook over alleged private message scanning and unauthorised use of images in advertisements. In addition, harassment and bullying, particularly amongst adolescents, has reached epidemic proportions on the site.

Whilst privacy and harassment claims are now commonplace, Facebook users have largely escaped defamation actions, especially when compared to their Twitter counterparts. The word "Twibel", for instance, has even become part of legal discourse to describe libel actions on Twitter (in the UK see Cairns v Modi [2012] EWHC 756 (QB); in the US see Gordon & Holmes v. Love, No. BC462438)

As far as we are aware, there is no equivalent term for Facebook libel cases. "Fibel" or "Libelbook" are both clunky amalgamations of words but we suspect that the lack of a "Twibel" equivalent is instead attributable to the relative dearth of Facebook libel cases, some of the reasons for which will be set out below.

Most Facebook users (72% according to Consumer Reports magazine in June 2012) select a locked profile so that their comments on their wall can only be seen by their connections: people with whom they have consciously decided to interact (either by adding a user or accepting a user's invitation). It can therefore be reasonably assumed that a user's connections on Facebook are either friends or acquaintances; at the very least they should be an individual whom the user does not find offensive (otherwise they would not have been added/accepted in the first place). In other words, enemies, or those harbouring grudges against other users, are not generally friends on Facebook.

When friendships cease to exist, users will often conduct what have become notorious Facebook culls: removing distant, offensive, annoying or boring contacts. Accordingly, many Facebook users' profiles will only be accessible to an up-to-date list of selected Facebook 'friends', the majority of whom, it can be assumed, would be unlikely to contemplate starting libel proceedings without first contacting the author, to resolve the matter in an amicable way.

A tweet, on the other hand, can be seen by anyone - provided that the user's profile is public (and according recent to research 88.2% are) - even if they are not signed up to Twitter. The badge of popularity on Twitter is awarded to those with significant followings and so many users are indifferent to the actual composition of their followers. Further, tweeters with a public profile cannot control who follows them initially but can, of course, block a follower later on. In any event, the blocked user can still view any public profile.

Reasons for following an individual on Twitter can be manifold; some might follow purely out of interest whilst others seek actively to troll ( according to a recent study by a group of students of PEC University of Technology, Chandigarh, has suggested that 15% of Twitter users are "malicious").

Thus it would seem that in most circumstances a controversial tweet is instantly subject to much wider scrutiny by an unfiltered audience than a comparable Facebook post. This could have a dual effect in terms of libel actions: first, the subject of a defamatory post is more likely to be made aware of its existence; second, there is a serious risk of the tweet going viral within the first few minutes of it being made, thereby potentially affecting the amount of damages for which a putative claimant will be able to claim.

In assessing the potential damage caused to a claimant in a libel matter, a judge will wish to see evidence that the publication is substantial. The potential for false allegations to be spread on Twitter, or what Andrew Caldecott QC eloquently described in Cairns as the "percolation phenomenon", means that the subject of a libellous post can be caused considerable reputational damage within a very short space of time.

Do privacy settings on Facebook then militate against this percolation phenomenon?

The recent High Court Facebook libel case of Walder v Smith - which we understand to be one of the first successful claims of its kind - makes clear that Facebook users are not in fact shielded by their privacy settings and that an ill-considered post can spread much further (and faster) than the author ever intended.

In this case, Sharon Smith, a fitness instructor, posted an untrue message about Joanne Walder on her private Facebook wall. Ms Smith had apparently only intended to send this message to one of her close friends but her mistake meant that it could be seen by all of her contacts. Her sister, Mandy Smith-Aichen, then reposted this message so that it was also visible to all of her connections.

It was estimated in total that at least 950 Facebook users saw the defamatory post, thus satisfying the substantial publication requirement for a libel action. It should be noted that the number of potential recipients more than doubled following Ms Smith-Aichen's repost.

The High Court granted a procedural judgment for libel in favour of Ms Walder following Ms Smith's failure to reply to the claim form and particulars of claim within the relevant timeframes. We understand Ms Walder is claiming more than £20,000 in damages and we await the outcome of the hearing on damages and costs.

At a time when Facebook appears to be trying to modernise in response to growing competition from other social media providers, recent changes have arguably meant that users have less control over what information is, or becomes, publically available. For instance, recently introduced cover images on Facebook can be viewed by any other user, irrespective of whether the most stringent privacy settings are in force. Similarly, commenting on, or "liking", material on the site might inadvertently result in this material becoming visible to all of your connections.

Whilst Facebook is perhaps regarded as a safer place to share material than Twitter, Walder v Smith demonstrates that the site's privacy settings do not guarantee immunity from libel actions. Cue further Facebook culls.