Though everything stated thus far seems to be based mostly on speculation, I can certainly see the roaming mass armies happening (and indeed already happening to some degree). I'm relatively new to this game, and not an avid player (pretty casual, I'd say) and spend most of my time building myself up rather than tearing others down, but in a single day, due to the repeated attacks of a single user, my capitol city was completely demolished of nearly everything. Definitely a frustrating experience, particularly since the individual decided to continue for about a week afterward.

If it does end up being thrown into such chaos, I'll try to stay as long as I can, most likely.