How many bytes in human memory? is a very brief article providing estimates of just that. Evidence from human learning experiments suggests that, after using a very good data compression algorithm, human long term declarative memory holds only a few hundred megabytes.

How much of that information is common knowledge, such as knowledge of the English language, memories from media such as books or television, or knowledge of local buildings and streets, is unclear.

Additional information specific to an individual could be gained from email, internet posts, and other personal electronic information and written records, such as diaries; as well as individual genomes, which will soon be ubiquitously available.

The modest information content of human declarative memory might be relevant to some of the discussions on this thread.