I know in Oblivion, you could be the Leader of the fighters guild, the arch-mage, the grey fox, the listener of the dark brother hood, and champion of the arena and no one would even know, or care, outside of members of that guild. (with the exception of the adoring fan xD)

But yeah, in Skyrim, if I were to say work my way to the leader of the College of Winterholm (I think thats right) will I still be able to join The Companions, or will they not let you due to your status?

I really didn't like the oblivion system for that, so I hope it changed.

You can do all of them at once

I don't think there is any ingame barrier from becoming head of them all. I suppose those who do not like being the leader of the free world will have to use self control to keep from joining things that they don't think it plausible.

That's gonna be a problem, aww well.

actually though it may not seem fighters and mages guild are friendly i''m not sure for skyrim (please dont tell me if it is)