I remember that thread we had not long ago where it gave out xbox live numbers and it left a 20-30 MILLION gap between total 360s sold and number of live accounts there were.
That's a lot of people to leave out in the dust with a forced connection feature.
And that´s when you assume that all the people that have a Live account are actually willing/able to deal with always online, which i seriously doubt.
Microsoft would be insane to pull this off.