Ok, he's my take on how the Bethesda E3 demo *might* work given the facts that
a) I've had the highly dubious pleasure of making these builds for four titles (Simon the Sorcerer 3, Call of Cthulhu DCoTE, Brian Lara Cricket, Operation Flashpoint 2)
b) I've had to stand there at trade shows and 'demo/drive' the stupid demo for journlists.
Roughly speaking there are two kinds of demo, ones driven (played) by the developers, and one that the reporters can get thier hands on themselves. Generally developers (or in Bethesdas case developer/publishers) perfer the first kind. Unlike a final demo, E3 Demos are built off the main branch development code, and and as such usually contain a number of known bugs, and general instabilities, and in other words are a work in progress...
So an E3 demo is nothing like a release demo you get on a mag. Why? well first the E3 demo usually an incomplete buggy engine with a bunch of hacks in just to get it working, with polished graphics. Developers HATE making them, as it takes time away from actually writing them game, but from a PR point of view they are a necessary evil.
As to will Bethesda allow the public to play the game at E3, I can't possibly say, I parted ways with Bethesda many years ago, but generally like many developers they don't allow the public to play their demo at E3 if they don't have to.
I hope that sheds some sort of light on the debate from a developers point of view...
