Social networks have clear rules on what posts can be deleted
But is all offence actionable? When does hurt or outrage translate into genuine bullying or abuse that social networks should remove? What is the difference between a robust challenge and an over-the-line personal attack? And should 'public' persons simply grin and bear more abuse than private individuals?
In some cases, a dividing line remains elusive. But social networks are now setting clearer boundaries on what they think can stay up versus what must be taken down.
Demonstrably serious threats, harassment or the posting of privacy-protected information (like credit card details or personal phone numbers) is generally against the rules for Facebook, Twitter and other social networks.
They will also remove reported posts that cross a certain 'shaming' line. Specific examples of this include so-called 'revenge porn', photos or videos of physical bullying or doctored photos intended "to shame a victim".
Facebook has also recently added an expanded set of rules of how it defines 'hate speech' and harassment, including some notable exceptions to it. It says that directly attacking people based on race, religion, ethnicity, gender, sexual orientation or disability immediately raises a red flag.
However, Facebook will allow satire or humour around these themes if the overall impression is not one of victimisation. It will also allow posts highlighting hate speech, if it's in the context of raising awareness about it.
Read more: 'One sordid, gross and offensive comment must have been thought up while he sat there scratching himself in his grey fading jocks. I wonder what makes people think it's acceptable to make comments like that?'
But there is another important distinction: is the individual targeted a 'public' or a 'private' person?
Like large parts of the media, social networks set a much higher pain threshold for what 'public' figures should be able to take compared to 'private' persons, "who have neither gained news attention nor the interest of the public, by way of their actions or public profession".
"We permit open and critical discussion of people who are featured in the news or have a large public audience based on their profession or chosen activities," says Facebook's recently updated rules. In practice, this often means that personal attacks - even those that might be hurtful to the individuals - will not fall foul of Facebook's publication rules. The same goes for Photoshopped images, although it does not go so far as to permit publication of hacked photos of naked celebrities, as happened in the recent Jennifer Lawrence nude-photo controversy.
Sometimes, this leads to very distasteful results. An online reality TV couple in Cork who broadcast the live birth of their child in 2012 had wishes of stillbirths and miscarriages sent their way. Jonathan and Anna Saccone-Joly put themselves in the public eye so they should suck it up, said some commentators.
Involuntary public figures can fare even worse. Last year, the parents of the missing child Madeleine McCann prepared an 80-page dossier of online abuse directed at them. One of the most persistent trolls, a 62-year-old woman called Brenda Leyland, was confronted by Sky News about her abusive tweets to the McCanns. She subsequently took her own life.
When it comes to getting content removed, social networks operate a passive system. Instead of screening everything themselves, they rely on users to report inappropriate posts, comments or images.
Reporting alleged abuse is usually possible through a button on individual posts. However, it can take 24 hours or longer to have the content looked at and adjudicated.
Read more: Protect yourself against 'catfishing'
There are a few things that anyone can do to limit their exposure to harassment or unwanted social media interaction. Blocking users is the most basic tool: most networks make it easy to do this. Reporting an abusive user is also relatively straightforward, although dedicated trolls can easily set up new 'puppet' accounts in minutes, especially on Twitter. Adjusting privacy settings to limit access to friends or other defined groups of users is also an option.
For really egregious abuse and harassment, Irish law has some remedies. Section 10 of the 1997 Non-Fatal Offences Against The Person Act makes online harassment an offence. Recent convictions have included a case where a man who impersonated his girlfriend on her Facebook account was fined €2,000 for criminal damage.
What of the European Court Of Justice's (ECJ) recent ruling declaring a 'right to be forgotten' online? The ECJ ruling applies mainly to search engines so its primary effect is aimed at search results that link to material that someone wants to have removed (though only from the search engine results, not deleted from the original source). This could help to limit the accessibility of unpleasant photos published on Facebook which are indexed in Google Images.