Our take
Trust is won or lost at the surfaces where a person hands you the most of themselves. What your product remembers about them, what you are allowed to keep and train on, who reviews the hard cases, and the rules you ship into. Each is a design problem, and each is easy to get wrong by keeping or doing more than you should.
Memory that earns its place
Memory is what makes a product feel like it knows you, and it is also where it can start to feel like it is watching you. Good memory stays scoped to the moment it was meant for, and it leaves the person able to see and change what you keep. More storage does not make a product more helpful, and often it does the reverse.
What you keep, and who checks it
What you store and what you train on is a sharper decision than what the product says back, because that data leaves the person's control and can resurface later. Keep it scoped, keep a real deletion path, and be honest about what feeds the next model. And put a person on the hard cases, because expert review is both the quality lever and the compliance control, and in guidance it is usually the same expert doing both.
The rules you ship into
The same care runs through privacy, data residency, and the regulation now landing in enterprise and healthcare. Design for those rules from the first sprint and you build a product buyers can actually deploy. Leave them to security review and they become a rebuild. Memory, retention, and governance are one promise, that a person stays in control of what the product knows about them and keeps.