Gene-sniffing USB devices become tightly coupled to dating (note that one doesn't need a website, you can take it wherever you go and it'll sniff people for you!); facebook gains as much of a monopoly on that as it currently holds in the online `friends' app world; using its vast data, it develops "social and epidemiological compatibility" algorithms; these algorithms form a feedback loop with advertising targeting and revenue; over a period of a few thousand years, Facebook's AI turns humans into separate Morlock/Eloi species, except there's one species for every main cluster of marketing type; in 4000AD, these human variations are paraded at the AI equivalent of Crufts.