I think my speculation that The Others on Lost are particularly interested in children with psychic potential was completely vindicated in last night's episode, "Three Minutes", but Anthony Martin suggests that perhaps it's size that matters.
I just realized why perhaps Walt was at the other terminal on the island chatting with his Dad, and why perhaps "the others" kidnapped all of the children.
The other facility had a near mishap, perhaps their blast doors have partially closed, which prevents adults from entering the dome to access the terminal. Only children are small enough to get in there and enter the code. That's why Alex was stolen from Danielle 16 years earlier. That's why the children were stolen from the tail section survivors. And that's why they attempted to steal Claire's baby, and of course Walt.
In other words, the other terminal is in a similar setup as the Swan facility, but the code is inaccessible by adults.
Personally I think The Others are pretty much in charge of the island, and we know now that they're "testing" Walt's abilities and not just using him to push a button.
As for the boat at the end of the episode, I bet it's Desmond returning for the season finale. He'll be pissed when he realizes that he's back on the island!