On Castle Siege and Delphino plaza: You know those walk-offs that appears after awhile (I could care less about water). That is the reason why we CPd these stages. Walk offs allow for characters like Dedede to chain grab someone, and allows characters like Charizard to Bthrow someone off, and a character like Squirtle to grab someone facing the boundary and use an Fthrow or Dthrow.
On Hanenbow: there are complaints of a mini loop made by Fox, but its real problem is that it is on the edge of being considered large, which means there are problems, but I personally have no clue why its banned, I just don't like it as much as PS2, which brings us too...
On PS2: I have absoloutley no Idea why this stage is banned. It is just annoying that's all. It is only slightly lower than it's counterpart, PS1, on the legal list, but they are solid CPs (PS2 means Pokemon Stadium 2, like PS1 means the original Pokemon stadium, don't think they stand for the playstation)
On Pirate Ship: Somewhere along the lines of bombs, an annoying catapult, an instant KO area, and that is all I can come up with, that is likely enough to ban it.
On Big blue: *HACK* that stage is definitely not legal. We banned it for the track and the track alone. Hit it, and you're practically dead.
On Corneria: There is a wall on the right side that promotes infinites.
On Shadow Moses: There is a dual problem with this stage. Early on, it is a place for easy infinites but harder KOs for those without a good/reliance on vertical KOs. After a Wall or two is destroyed, there are walk offs, which promote the reasons Castle siege and Delphino plaza are CP.