I think I know why Jack , Kate and Sawyer were taken . First , why weren't any of the other losties taken ? It is safe to say that the "good" ones were not taken or Echo , Rose and Locke ( since I'm the only one here that doesn't think Locke is good) would have been taken and Sawyer and Kate would not have been . Then if they wanted those that posed the biggest threat to them , Saied and Locke would have been included .

Therefore , I think Jack , Kate and Sawyer were taken B/C the others still want an infant when it is first born and they have been watching the group and know that Kate is attracted to both Jack and Sawyer and believe that she could/would be with either one of these two men and possibly conceive a baby that they could have and do what ever they intended to do with Claire's unborn child . I wondered why they didn't just steal Aaron later , but now I'm pretty sure they only want an infant , pure or uninfected or whatever ............... any comments ?