This talk focussed on the change in the social aspects of the game in WoW that had occurred due to the implementation of phasing. Phasing allows players who are at different stages in the game see different things at the same physical (physical? in-game?) location. Apparently previously the game felt slightly unsatisfactory, as the extreme effort that went into kills or completing quests never had any lasting effect on the game world - the killed monsters just respawned, and players had to bend their internal stories to fit this situation. Phasing changes that.
Other benefits include adding some protection for the noobs (like me!) because experienced players can't see the areas in the same way that the noobs can and therefore can't attack them. It does also explain why I felt the world seemed a bit empty in my initial explorations.
Apparently it is this inability to see characters at other levels that has had the biggest effect on the social side of the players - they can't interact in the same shared space any more, which puts a serious limitation on the amount of sharing players can do. It could also highlight one of the problems suggested in 'Alone together' as a reason why guilds fall apart - players who started out progressing at the same speed but fall behind at some point will no longer even be able to see their guildmates on screen. Quite odd.
Interestingly, Torill did say there were cases where it added to the story of their characters. She gave the example of one particular area, where after completing the quest you hear screams of the dying. Her guildleader hadn't completed the quest, so couldn't hear the screams. It added to the impression of the character as haunted by their past!