I say that the bear is on the island 'cause Dharma is seeing if their new hybrid will be able to adapt to the new climate. Poor polar bears IRL aren't adapting very well... as of this summer they are now an endangered species.
Maybe that's why Dharma has taken the ever-loved trio. They're gonna mutate them. They'll become the Island X-Men! Yay! Sawyer will have the power to use his profound vocabulary to sucessfully manipulate the minds of others around him (kinda like Hitler), Kate will have super speed, and Jack will be able to fix any boo-boo with his brain! Yup. Another LOST mystery solved by yours truly.
But I think the problem is mostly just props, but I love speculating about these things. Let's you see both sides of an issue. And it can lead to some very interesting conversations... lol.