![](http://gallery.lost-media.com/albums/ep-caps/season3/3x01-cities/4/normal_twocitiescap-0915.jpg)
From another listener on Lost Unlocked: The listener theorizes that the Others use time travel to travel to the time and places of the LOSTies pre-flight 815 in order to compile their files on them. This explains how they know that Sawyer killed a man before leaving Australia, something the Australian authorities did not know at the time of the flight. It also explains how they know that Sawyer's "Sawyer" is actually Anthony Cooper. The theory also led to a real chicken and egg conundrum as they further theorized that the Others or perhaps someone else like Widmore manipulated the 815ers onto that plane on that date, an interesting variation on a theory that's been out there from the beginning.
I kind of like the idea of time travel being used to determine who the 815ers really are. There are certainly those who believe that explains Richard Alpert's appearance in young Locke's life. It could also explain the speed with which they compiled the information if you can leave time x on the Island and return to it with no time passing. I like that it restores some of the mystical and mysterious nature of the Others. But I suppose it could equally be a network of PIs Off Island.