The answer is...
Only people who have been to tournaments before should post here. If you haven't been to a tournament it's likely you don't know what your talking about.
I've been to several large and small tournaments, and placed in the top 10 multiple times (my best is 4th). And I still say FS's should be allowed, at least at first. As I stated before, anyone familiar with the history of the tournament scene will note that items were allowed in most tournaments for quite a while. Many tournament organizers agreed that some items would still be allowed to this day if it weren't for the fact that turning on ANY item makes the unfair exploding capsules appear as well.
Smash Orbs is the fairest item I've seen. It floats away when you hit it. It is on-screen for a while before anyone can hit it, so everyone has some opportunity to decide to go for it or not (it doesn't just appear right above your head like other items). Even if you were in a position of power (and good for you if you are, you deserve some benefit) when one appears on the stage, you'd have to give up on your edge-guarding to go get it, leaving the edge freely available for you opponent to recover. Or, you could continue to edge-guard but risk them getting past you and now you missed your chance for the smash orb. It takes a while to get, so once you decide to go for it your opponent has opportunity to get close to you and try to get it themselves or ignore it and smash you while your attention is diverted. It has a balancing factor of speed vs power characters being able to get it (since speed characters get to it faster but power characters can break it open in less hits). You are vulnerable to getting killed by your opponent while your attacks are focused on the smash orb. Even once gained, you are vulnerable before using it and risk having it stolen, but if you use it too soon you could miss entirely and waste your advantage. For many characters, you are vulnerable when using it as you are locked in place for quite a while. For other characters, it provides a balancing factor as intended by the balancing the devs are doing to help an otherwise weak character by having a particularly effective Final Smash.
The argument that it is like a starman is lame. Starmen DO appear right next to you, and they only have to be touched to be used, at which point you are invincible. Smash Orbs have to be attacked, they float away from you when hit, they leave you vulnerable while trying to get them, and they don't make you invincible (at least not until you have a chance to use them, and that only applies to some of them). In any skilled matchup, they aren't necessarily a free stock either. Its obvious to those of any skill level watching the videos that most of them can be avoided fairly easy, you have TONS of warning before they go off. And, of course, Starmen do the same thing to every character. They do not affect character-to-character balance, they just randomly affect the match. FS's are different for each character. They are part of how characters are balanced with each other. If everyone had the same result when a FS was used like a Starman does, I'd be much more likely to say go ahead and ban it, but since they are different per character and part of the uniqueness and power of each character, its not the same thing at all!
To me, banning FS's changes the balance of the game, and would be about the same as banning Fox's reflector, or Samus's charged shot, or Jigglypuff's rest, or Marth's side smash, or Peach's down smash, or banning Shiek altogether (as would happen with ZSS). Yeah, those moves are powerful and I honestly wish we could ban some of them. But how do you think players of those characters would feel about those moves being banned? By the same token, if a player has a character that is otherwise fairly mediocre but has a fairly effective Final Smash, and they have developed mind games and tactics involving their Final Smash in their training, how will they feel if their character is bumped from mid/high tier to low tier by banning them from using one of the core moves of their character?
We're not talking about some glitchy advanced technique like wobbling or Ness's jackets or something here. We are talking about a core move that any player can use being completely taken away from their character. Might as well just ban Smash attacks or spot dodging or all reflection B moves! Its clear that from the devs point of view, Final Smashes are now as much a core part of the gameplay as these other basic moves. They are MUCH more integral to the character balance in Brawl than the other things we've banned from tournaments, and MUST be considered much more carefully, based on actual gameplay, rather than the quick and rash opinions I've seen from many posters in this thread.
I believe tournaments should allow FS's at first, and see how it goes. If some find them distasteful after giving it a shot for a while, I believe the tournament scene will split into two types of tournaments - one with and one without FS's. Perhaps even have single tournaments with 2 brackets, one with and one without. I imagine the tier list will be different between the 2 styles due to the reasons I mentioned above, so we'll likely need 2 tier lists if those opposed to FS's still feel the same way after trying them out in a few tournaments.
Of course there's the possibility that everyone will agree after giving it a chance that FS's should not be in tournaments, but from what I've seen so far, and keeping in mind the skill level of the players in the videos, the many mindgames and meta game components FS's offer, and the vulnerabilities inherent in their use, I doubt the tournament scene will be completely rid of FS's for several years at the least, if ever. The community will express disatisfaction with tournament organizers enforcing a rule that half of the player disagree with, and you'll find the tournament organizers are quick to change their rules when they get that many complaints.