For example, in 17th-century England, most people lived in rural communities of 100 persons or less, and if two unmarried people were caught having sex, they were whipped until bloody and cast permanently out of the area, isolated from their friends and family.
In 19th-century England, 200 years later, most people were collected in towns, and London was the largest city on earth. Urban residents did not have to take a personal interest in the social lives of their neighbors to ensure the stability of their own lives, and even if they wanted to, strict rules of sexual conduct were much more difficult to enforce.
Now we're on the edge of another leap in accessibility: Database-driven location-aware matchmaking sites.
How are these going to affect sexual morality?