From the Q and A with Paul Sage

Originally posted by Wrehn
How does the mega server actually work as far as intelligently assigning channels? Do we fill out a preference form, or link our facebook account?
Tell us more about the end game, cyrodil, and instanced public dungeons. I just wanted to know what's in store.

Right now, it uses data we already know about you. Your in-game friends, your guild associations, etc. We take that and try to put you in a channel of people you most likely want to be with. We talked about doing a form at one time, and we still might, but that isn't in right now.

That's a load of questions. Let's take end-game:
PVE
Solo end-game = what we have internally been calling 50+. Imagine you can go into any alliance after you complete the zones in your original alliance, but there are no longer levels. Now you can go anywhere you want in that alliance. If you finish that, you go onto the third alliance.
Small group end-game: Master dungeons. You'll go through dungeons which are more difficult to do progressively. Also we have Adventure Zones where there are large swaths of area just for the smaller group. (4 player)
Large group: Adventure Zone instances. While we aren't calling them "raids" internally, that's what you might be safest in imagining.
PVP:
Caters to groups of all sizes. But this is Cyrodiil, a huge land mass where you can just adventure solo doing quests, or looking for resources. Maybe you want a strike group to take out farms or mines. Also you have large objectives like keep sieges. The beauty of Cyrodiil is the size allows for lots of different sizes of group activity down to solo. However, we do pinpoint the hotspot on your map for you, which means if a sizeable fight is going on, you will see it dynamically appear on your map.


"Can you imagine that how it will be if all your online gaming friends who play TESO, are all gold prospectors?  Everybody grouped in the same channel.  What are your thoughts on this?"

Dano