The concept of file ownership/permissions != DRM... file ownership/permissions are supposed to be a way to stop you from getting owned - the concept and implemnentation it's a simple method of sandboxing dumb users or poorly writen applications from writing to places it should not be able to. Every modern operating system does this.
I think you miss the point that he is making, with any process/application to be able to write to any other process or application, it creates a completely untrusted environment where you cannot expect the system to be in any state when you cannot completely control it's inputs. Combine that with many alternatives available that are more secure/sane by design, there aren't many uses for it...
Sure maybe it can go in a stand alone video editor... but why would you when you can put linux on that same machine and connect it to the internet/render farm and not have to worry about it getting pwned in a javascript buffer overflow