You'll see an example of the effect of the decree above. That's a portrait of the Emperor Septimius Severus and his family, including his wife, the Augusta, Julia Domna and their son Caracalla, himself later emperor, most famous probably for his Baths. You might notice the large dark spot under Julia's face. There used to be another face there, that of their son Geta. For a brief time, Caracalla and Geta ruled together after their father's death. That didn't turn out well for Geta. His brother had him murdered, and then as sole Augustus convinced the Senate to issue a decree of Damnatio Memoriae to remove him from history as he had been removed from this Earth.
Of course, if the intent of the decree was to erase someone from memory, or history, it didn't work in the case of either Sejanus or Geta. We know well enough who they were. It's likely, therefore, that the intent was not to do so but to instead deprive them and their memory of all public honor and esteem. Such things were important to the Romans, and to the Greeks as well and Hellenistic and Greco-Roman society. The notion of the afterlife wasn't particularly alluring or vivid to the ancients. One's immortality was assured by undying glory and monuments to fame.
The Romans were not the only people who engaged in this practice. Most recently the Soviets tried something along these lines. Stalin did his best to eliminate some of those who were his rivals, real or imagined, from the history of the Russian Revolution. An effort was made to do the same with him, in a minor way, as to the history of the Soviet Union. When one has control of the methods by which reputations are made or unmade, and where one is an autocrat, there must be a certain
satisfaction in doing this to enemies, or it may be that it is advantageous in various respects.
What seems to have been an impossible task even in ancient times is certainly impossible now, as we leave our marks everywhere in photographs, records electronic and otherwise, on the Web, etc. nearly ad infinitum--whether we do so voluntarily or at the behest of someone else. Or so one would think. Might it actually be easier now than before, at least if the idea is to hide someone from those who lack the knowledge to determine when a person's name has been deleted from the Internet or electronic records and how to receive that information? Now that we live online, the ability to control what is or is not online takes on a particular importance. What is or is not online may be all or most of what we know or can learn, or what we want to know, perhaps very soon.
If, though, we can't "erase" someone from history, can we insert someone, or some unreal someone, into it, especially now? There are instances where people have believed in the existence of a fictional, fabricated person in the past, but perhaps it may be easier now to create an identity or at least a more detailed, ubiquitous person that we could in the past. Human, face-to-face contact is becoming increasingly less important, less necessary. We can fake personality and likeness with remarkable success these days.
Ah, the disturbing wonder of these times. What a time to be alive.