I didn't catch the promo, but I can see Danielle doing that.

I don't think Charlie is working for the island. The island didn't give him anything - except Locke, who made him get over his addiction and found his guitar. Also, Locke getting the use of his legs back was miraculous, whereas Charlie getting over his addiction was just plain hard work.

So, why do you think Locke started losing the use of his legs on the episode where he and Boone found that plane?