Check this out:
http://www.youtube.com/watch?v=_RSPe_qlDMU
Samus gets Final Smash capability without ever getting a Smash Ball. How? Apparantly, according to demo players, if you are doing very badly then when you respawn, you will have Final Smash capability already turned on without having to get the item.
Do you realize what this means??
This feature is evidence that Final Smashes ARE considered different than just an item in the coding of the game. The fact that
you can get a Final Smash without any item being involved at all shows that they are a much more of a key element of what makes Brawl what it is than just being a powerful item, akin to Supers in SF3. It also shows that there is a chance they cannot be turned off at all, since there's no guarantee that even if you can turn off the items in the items menu that it would turn of Final Smashes themselves being granted to losing players for free.
I'm beginning to think it is quite reasonable that many tournaments will have items turned off but still allow Final Smashes, due to how integral they are to the game's design and due to their effect on character-to-character balance (which no other item really changes significantly, no matter how powerful - other items give nearly equal benefit to any character that gets it, but a Final Smash is unique per character and part of what makes up that character's moveset).
If FS's are turned off, is it really Brawl any more at that point, or just an attempt to recreate Melee?
Important to also consider is the effect Final Smashes would have on tier lists. Banning them could affect character power balance the same as if you banned, say, Side+B moves, where some characters would be largely unaffected but others would be severely hampered. It may be necessary to make 2 tier lists for Brawl, one with and one without Final Smashes, with tournaments that support both modes (again, assuming you can turn them off at all, which this feature casts some small doubt on). At least until the community has a LOT more time to test their impact in the competitive scene.