Rated Battlegrounds will share Conquest points and rewards with the current Arena deathmatches. You'll need to enter the queue as a full group to qualify - thus ensuring some kind of responsible chain of command - but teams don't need to be set as they do in Arenas. There'll be a cap to the number of Conquest points you can earn in a week (it goes up with your rating), so there's no pressure to do both Battlegrounds and Arenas to maximise your income - as Street says, it should be a genuine choice of preferred playstyle.
There's a correlation there with the changes to raiding, where Blizzard wants to encourage - or rather, force - players to choose between 10 and 25-player raids rather than wear themselves out trying to do both. Shared lockouts and item rewards at the same level across both should take care of that, although some raid fanatics are sure to wince at these new rules. However, there's more flexibility to balance them: a 25-player raid in progress can be broken down into up to three 10-player raids, should attendance cause problems, while players can actually move between different raids on the same lockout, as long as they're not joining a raid where they've killed bosses the rest of the group hasn't.
It sounds a bit of a tangle on paper, but the aim is to make raiding a friendlier and less demanding experience overall, and easier to do in less organised pick-up groups. "We want a raid to be a raid," Afrasiabi says simply. "We don't want you to feel obligated." We certainly won't feel obligated to check out Skywall, a drop-dead gorgeous raid and dungeon zone sitting on soft clouds in the Elemental Plane of Air, where you'll need to use your own flying mount to skip between floating chunks of architecture. Its pastel, painterly backdrop must be the most beautiful skybox ever.
Last, but most definitely not least, is Cataclysm's new guild levelling. Again, this has been pared down slightly from the BlizzCon vision, but only very slightly, with the idea of guild talent trees - which would really only have been fun for the leader - replaced with a linear trail of convenience Perks that unlock every guild level. They might be experience or mount speed boosts, reduced repair costs, or mass resurrection or raid teleport skills, and everyone in the guild can use them.
That makes being in a guild sound attractive, but the really important part of the equation is to tie the player to the guild, to mitigate against fickleness or even the sale of advanced guild profiles. This is achieved by every player having a reputation level, just like faction rep, with their own guild, which is advanced by killing bosses, earning guild achievements, winning in PVP with guildmates by your side, or questing. Advancing in reputation unlocks special guild rewards from a vendor (bank slots, flying mounts, standards with a guild emblem). All this is supported by a quasi-Facebook guild pane complete with news feed and browsable roster with links to guildmates' profession panels.
Can you really turn gameplay systems into social glue? Blizzard hopes so, for the simple and inarguable reason that WOW is more fun in a guild, and guilds are more fun if they stick together. People who already enjoy guild play certainly won't complain either way about such a transparently well-thought-out way to level together rather than alone.
Taking a guild to the level cap is yet another journey in Cataclysm - alongside the new races' sparkling introductions, the epic level 80 to 85 zones and of course the new road through old lands that is the route to 60. Unlike the others, though, it's one you have to do with friends, and that might make it the most important of them all.