Will main quests be instanced seperately for each player, or will I be able to do them with a friend who is at the same stage of the MQ as me?

I wonder this as well but from what I saw on the forums people say that the MQ is a single-player experience? Let me know if im wrong, I hope so.

Dont think there is much info yet but i seriously doubt that that will not be possible!

So far we know that the main quest line is solo-able according to which sources I forget.

However I think the operative phrase was you CAN solo the main quest, not MUST do it alone.

Correct me hastily if I'm wrong though.

Yeah its a MMO, it would be silly if you could not play the story content cooperatively, or at least be able to help someone with his quest.

sweet. As part of me and my friend's RP, our characters work together, and their descendants in the "future" TES games

take a look at SWTOR then...
GW2 also was solo instanced for most story parts

and ESO since is made for the same mass market I'm pretty sure that the main story line will be single player only.

I've played every class story twice to the end in SWTOR. And you could aways get someone to join you whatever the quests.

The instanced story parts were only validated for one only player a time, so if your teammate was the same class than you (and so needing the same story quest), you had to perform the part twice. Once for each. But never at anytime where you forced to solo any quest.

At this moment I'd advise you and your friend to make the same decisions so you're in those same phases together.

We're planning to do all the MQ quests together, making the same choices etc