Domenico was shot dead along with his mother and her partner when the car they were travelling in was attacked by gunmen in Taranto on Monday, sparking reactions of horror in Italy.
Two other children in the car apparently only survived because they played dead.
Investigators said the woman - the widow of a murdered mafioso - had provided information which led to the arrest of several criminals while her partner, himself a convicted murderer, had been taking advantage of day releases from prison to try to regain control of the local drug market.
Italy's best-selling daily, the Corriere della Sera, described the toddler as one of a string of "defenceless victims of the men of dishonour", such as three-year-old Coco, who was shot dead in the arms of his grandfather two months ago.
Their murders follow other notorious deaths, such as Giuseppe, 13, who involuntarily witnessed the assassination of a trade unionist in 1948 and was murdered by an air injection while in hospital.
Or 12-year-old Giuseppe di Matteo, the son of a mafia turncoat, who was kidnapped in 1996 and kept in atrocious conditions for two years before he was strangled and his body was dissolved in acid.
"The idea that the mafia does not kill children is a historic lie...cultivated over a long period with care by the men of dishonour," writes Goffredo Buccini in the Corriere.
'Disorderly rise of new killers'
Today, "the crisis which has pushed the old bosses to reinvent themselves, the disorderly rise of new killers, the use of drugs which burn souls and hearts, mean killers no longer have the time or possibility to hide their real faces", he said.
The fact that "children don't get hurt is a myth, broken as early on as the post-war period," said Francesco La Licata, mafia specialist with La Stampa daily.
Giacomo di Gennaro, a sociologist specialising in organised crime and criminal law in Naples, told AFP the violence has got worse since the arrest of the big mafia bosses over the last 15 years.
"These 'men of honour' used to forbid the killing of priests, women and children. Their control over the territory was so strong that it was not necessary. Today, the boundaries of territories change so quickly... all lines are crossed," he said.
He also brushed aside attempts to distinguish between the different branches of organised crime in Italy, from Costa Nostra in Sicily to the Camorra in the Naples region.
The Sacra Corona Unita in the Puglia region, where Monday's attack took place, had been held up as less violent than the other groups, presenting itself as a "protector" of the people.
On Friday, Pope Francis will meet in Rome with around 700 families of mafia victims, while on Saturday the names of 900 "innocent victims" of the mafia will be read aloud at a ceremony to mark a day of memory held by the anti-mafia Libera association.
"Italy's collective memory is short, very short, so we always pretend to be surprised, to be left speechless by the murder of those like Domenico," La Licata said.
"One thing seems clear: looking through the list of victims it becomes evident that this is not a country for children, or women," he said.