Hypothetical unless you count the IRC and IM logs, which I already employ for many of these purposes. To be exact, I'm saving funny conversation snippets to a separate file, recording past conversations, and reverse-engineering arguments. I've also done a bit of the saving good moments bit, though less than I could.

You do it too, you record everything with your brain. Sure, right now it is hard to read-out and memories are still vague. But the time will come when we'll be able to download memories. And that memories are vague and sometimes counterfactual will be even worse because people will believe them based on the persons credence. Further you are effectively speaking out against transhumanism with this stand. You are going to hate all people with advanced memory enhancements? You are going to hate all people which possess brain implants?

Anyway, what are you going to do the day when reading-out memories will be easy?

Identifying natural images from human brain activity

A challenging goal in neuroscience is to be able to read out, or decode, mental content from brain activity. Recent functional magnetic resonance imaging (fMRI) studies have decoded orientation position and object category from activity in visual cortex. However, these studies typically used relatively simple stimuli (for example, gratings) or images drawn from fixed categories (for example, faces, houses), and decoding was based on previous measurements of brain activity evoked by those same stimuli or categories. To overcome these limitations, here we develop a decoding method based on quantitative receptive-field models that characterize the relationship between visual stimuli and fMRI activity in early visual areas. These models describe the tuning of individual voxels for space, orientation and spatial frequency, and are estimated directly from responses evoked by natural images. We show that these receptive-field models make it possible to identify, from a large set of completely novel natural images, which specific image was seen by an observer. Identification is not a mere consequence of the retinotopic organization of visual areas; simpler receptive-field models that describe only spatial tuning yield much poorer identification performance. Our results suggest that it may soon be possible to reconstruct a picture of a person's visual experience from measurements of brain activity alone.

However, the idea that someone would want, or even tolerate, to be taped during private emotional moments and in situations where funny stories are told and passionate arguments made honestly baffles me. (With a few traditional exceptions like taping family events for sentimental purposes etc.)

Status quo bias?

A lot of people would probably dislike the idea of being recorded (which I think ought to be respected), though I suspect folks would get used to it. People already save emotional e-mails and logs of very private instant message conversations without others objecting, though obviously those have more deniability value. It's much easier to write an e-mail and claim somebody else wrote it, than it is to forge an audiovisual recording of them saying something.

In general, my attitude towards people saving logs or e-mails is that if I trust them enough to tell them whatever it is that I'm telling them, then I also trust them not to make the recordings public in a way I'd disapprove of. My attitude towards somebody lifelogging me would likely be similar.