If the user does enter a response, the conversation then appears in the user's News Feed, where the brand starts to reap "earned" impressions among that user's friends.

The most impressive change was the new advanced filters, which made it a lot easier for users to create streams based on keywords, groups, sets of friends and more.

What also struck Dr Marlow, however, was that the number of people on an individual's friend list with whom he (or she) frequently interacts is remarkably small and stable.