External Memory
I believe that the External Memory section should be broken into two separate sections or more firmly defined within the same section. One on "Self Identity" and using external objects to identify one's self, and "External Memory" being stored memories and information. Here are my reasons.

Self Identity:
In "Stand Alone Complex" Episode 25, Batou says to Kusunagi about her watch "No matter how many prosthetic bodies you went through, this was the one thing that was always ticking away the same time as you, right? In this time that's far too fleeting, people entrust memories to external devices because they want to set down proof that can identify them as a unique individual. For you, isn't that watch the one external mnemonic device that can identify the person you've been up until now?"

This says that external mnemonic devices are to create a sense of unchanging self in a world where you can switch physical bodies on the fly. As biological humans our forms are fixed and unchanging for the most part and our self identity is tied deeply with that. In the GiTS universe, that is not true and you must tie your self-identity to external objects such as a watch or weight training to distinguish yourself from the rest of the identical mass produced cyborg bodies and create a sense of individuality. There are references in SAC 2ng Gig Episode 8 about cyborg food satisfying the brains cravings and as a reminder of times before becoming a cyborg. In SAC 2nd Gig Episode 11 there is a store that keeps and maintains external mnemonic devices that remind their owners of their own personal memories. All of these "external mnemonic devices" are used to trigger memories in one's self, but can not relay detailed information to a stranger.

External Memory:
External Memory is exactly that, memories and experiences that are stored "offline" onto a hard disk or such. If you posses a cyber brain, there is a definite separation of mind and body since your brain case can be removed and put into a new body. Since there is an electronic separation, the signals received from the senses (touch, taste, etc.) can be recorded and replayed at any given time. Thus, you could record important events such as your wedding day and replay it as if you were actually there anytime you wish. Your external senses turn off, and you’re fed recorded sensory information. Better than any video camera recording, your feeling the heat of the sun, the breeze, your brides’ hand trembling as you slip the ring on her finger, etc. Storing these memories also allows others to play them back and experience them as well. This would be a highly valuable technology for all areas of use; fully immersive gaming and movies, virtual business meetings that feel completely real, instantaneous access to wikipedia anywhere. In SAC 2ng Gig Ep 23, Batou talks about using Kusunagi's external memories to keep Gohda talking in Ep 22. He also talks about peeking at her external memories regarding Kuze. In SAC Ep 10 Ishikawa experiences Batou's memories from the murder scene. SAC Ep 21 the whole team replays Togusa's memories from the Sunflower Society office when he was shot.