There are quite few mmos made almost entirely in flash, but mostly those are series of windows or frames, on which variables are changing, and nothing really happens OR interactive chatrooms divided to small rooms.
Games like Transformice are proof that you can make a good game with just a good interactive chatroom, but we've seen things like Doom Flash port and several other 3d games in flash, and it makes me wonder how capable flash is of running a "huge" game.
A simple MMO like Tibia or MU Online with big maps and lots of players fighting with lots of mobs at the same time, where every tile is an object - is something like this possible to fluently run on a flash client?
Also, are programs like SmartFox server and so on good for anything like that? Or a huge map with thousands of objects just being floor isn't just good idea no matter what You use?