I say that there are more stations on the island.
In the "Orientation" film they mentioned zoological experiments which explains the shark and the polar bears. Tests were being run on the island but somehow something got messed up in the process. Which caused the Scientists to go a bit looney. The Scientists then became "The Others". The reason they are after Walt? ESP. They know he has some sort of gift so they want more experiments to be done. Now some of you may be asking....how did they know Walt was coming and how do they know about his "gift". Not sure but look at this....
http://thetailsection.com/images/dharma-1.jpg. Looks a bit like the Dharma logo doesn't it?
Sun's father is connected somehow to the Hanso corporation. Jin knows more than he is leading on to. That is why he is "being punished" or whatever he kept saying to Sun in season 1. And hell...dude speaks english next episode according to the preview.
if you do a google search for "Hanso" it will pull up a website. mess around in there and you will probably get some more hints or it will spawn more theories.
Also, the others didn't throw michael, sawyer, and jin in the pit...those were the tail end survivors. they are just as confused as everyone else on the island.
Anyone remember what the firm was that Walt's mother worked for? I wonder if they are tied into this somehow and thats how they knew about Walt.
I know this post is all over the place, but im just typing as i am thinking.