I had no idea some players on MTGO solicited assistance from the twitch stream in playing their matches. I'm quite disappointed this kind of behavior is going on, and is considered acceptable.
When I log into MTGO, I'm expecting to play a single opponent, not a hive mind of a dozen pros. That is what a game of Magic is supposed to be about: a battle of wits between two players. How those players chose to prepare -- by playtesting in a team, reading Steve's Gush book, etc, doesn't matter to me, but when it comes time to shuffle up and play the game, I expect to be facing my opponent (and whatever level of preparation they bring to the table) and nobody else. I can't think of a single other game or sport where it's acceptable for arbitrary third parties to jump in and help one of the competitors.
Now if a player asks permission at the start of the match to involve their twitch stream, I probably wouldn't mind (except at the Daily level of competition, or above -- here I think it is completely unreasonable, and tantamount to cheating, to bring a crew of pros to help you win the tournament). But I'm completely opposed to a culture where outside assistance is allowed as a rule.
Whether or not a prohibition is enforceable is, in my mind, a red herring: behavior can be unethical, unsportsmanlike, and considered unacceptable regardless of whether it is possible to detect in every instance or not. For example, Slow Play in paper magic is impossible to police objectively, and if you decide to seed your FNM draft pool with a few commons and uncommons every week, you have a very high chance to get away with it -- yet I hope we can agree that both of these behaviors should have no place in sportsmanlike play.