I was thinking of Carl (Alex's boyfriend) and where he came from and that got me thinking about where all of the Others came from.
My initial though was that Carl must have been born around '88 just like Alex. However, we're all thinking that the childbirth problems have happened by then. So were did he come from? He tell Sawyer that he remembers being a young kid on the island after they both leave the Hydra station. So were the others still sending women off in the sub to give birth. I dont' think so. Why would have Juliet watched so many mothers die then if they could just leave and come back (this poses the other question of 'why didn't they just use the sub instead of let women die,')? Was he also kidnapped as a child?
It seems we've seen a lot of Others, and most of the one we know didn't start off that way. Here's my list of how Others gains members, please add to it and speculate.

Recruted: Juliet, Locke
Kidnapped and assimilated: Alex, Cindy, Zack, Emma, other Tailies
Switched Sides: Ben, possible Ethan and Mikhail
Origanal (pre '54): Richard, Jacob
Spirits?: Christian (speaks and works for Jacob)

Well we have no idea when the child birth problems happened.

Ben recruited Juliet in 2001, and it seemed like this was one of the first steps the others had taken to try to fix this problem, so it might have happened shortly before this. Or maybe after the purge.

My guess is Karl is either an original hostile or a member of Dharma that is born around '88 and then taken by the hostiles before the purge.

My impression at the time was that, although D.I. seemed to have no problem ferrying people to and from the island, the others seemed to use it only as a last resort. We saw Locke tell Ben that they shouldn't be using it at all. Plus, I think that Ben needed to solve the on=island birth issue by any means necessary. That's why Richard personally went to recruit Juliet. They were willing to give her whatever she asked for to come to the island and solve the fertility problem. Wasn't she the only new recruit on the sub? Resorting to taking women off island to give birth wasn't adressing the real problem. Which is that after the "war", there won't be any anything left BUT the island! Hmmm, I might be on to something here. I'm going over to the gen. theories board to flesh this out. And, yes, I'm taking a helmet.