“This is really going to impact institutions that we take for granted,” Internet Archive director of archiving and data services Jefferson Bailey told the Standard, “like our museums, our historical societies, our public libraries, our academic libraries — just a lot of people that keep information free and accessible and online.”
I think the real point of the adage, “once it’s on the internet it’s there forever” is more about the fact that you, personally, can’t take it back. Someone might of screenshot, downloaded it, reuploaded it elsewhere. The real meaning being that, once it’s on the internet, you no longer control it. Which I think still holds true, but it definitely was heavily implied that it would be there forever.
Pretty much this. Once you put it on the internet it’s out of your control. It might disappear, it might not. Best just to assume it won’t. Unless it’s useful information, then it probably will.