I guess it's good that the Darpa Lifelog project was quietly cancelled as this Wired News article, Wired News: Pentagon Kills LifeLog Project notes.
Lifelog's intent was to gather everything a person says (emails, phone calls, etc.) and does (air tickets purchased, television watched, movies seen, meetings taken, etc.) into a single data directory. The rationale is that:
the all-encompassing diary could have turned into a near-perfect digital memory, giving its users computerized assistants with an almost flawless recall of what they had done in the past.