After digging in I understand, gameplay wise, why they went with the small cities. The idea is to play multiplayer and rely on each other to make a super region and if everyone can just make crazy huge cities there is no incentive to do that.
BUT, I think Maxis was completely off the mark here. I, personally (and judging from this post neither do a lot of you) get any joy out of making my city have a lot of dumps so my friend can have a lot of hotels - or whatever. We would all be much, much happier with a 16 player map with HUGE cities and just build our own stuff... trade if we really need to... and just chat and check out each other's stuff. That's all I want. That would be awesome.
Small maps and forced cooperation are not awesome. I hope Maxis rectifies this, quickly.