Historians must have a interesting time. Or, they will. The sheer volume of recorded information generated in a person's life must still boggle their minds every now and then. Oh, I'm sure they still face all the usual challenges of obtaining the data, but to imagine it. These people carried a device, you see, that tracked their every movement. It also tracked what they were reading, who they were talking to, what they were saying...everything.

Plus, since every society that ever existed has collapsed, they will have an amazing level of insight into what exactly happens right up to that point. 

The greatest predictor: memes.