Dates in the history of modern social "media memory":
1837: photo memory
1876: audio and moving images memory
1996: web sites memory (archive.org - currently contains 150 billion pages)
2004: web search memory (Google trends database)
We also have now spatial locations and spatial trajectories memories (for both humans and cars) but they have not been exposed because of privacy concerns.
Interestingly, in this history science is relatively behind: dense sensor nets which capture data about climate etc. are rather recent. Of, course less dense measurements have been kept longer - for example, first "reasonably reliable instrumental records of near-surface temperature exist with quasi-global coverage" start in 1850s, i.e. around the same time as "photographic measurements" of human society.
Of course, these technological social records are very uneven in relation to time, location, type of media, and what has been captured. How "much" human life has been captured since 1840s? What percentage of the existing recordings around the world has been digitized? Interesting questions...
P.S. Note that I did not include text records in the timeline - books, birth registers, diaries, sales catalogs, etc - because humans used variety of technologies in different periods and places, so its hard to compress into a few dates.