When captives are forced to build a runway in season three, expect a plane to crash land on it in season five, lol.
My thoughts on who Sayid shoots--Sayid cannot kill Young Ben in 1977 because we already know that Ben grows up to murder his father in the Purge and become the leader of the Others, etc. Maybe Sayid injures young Ben and Juliet takes care of him, causing grown up Ben to be obsessed with Juliet upon her arrival because, as was said, "she reminds him of her."
Her being the future version of herself that Ben already met thirty years ago.
Whatever happened, happened. Trying to keep it from happening in the past will only cause it to happen.
But it will be interesting to see how much prior firsthand knowledge about the Losties that adult Ben has been carrying around since childhood (much like Widmore and Locke). Both Richard/Widmore and Ben had been preparing themselves for their eventual meeting of the 815 survivors for years, because they had already interacted with them and knew they would arrive. Richard gives a compass to Locke, who goes back in time and gives the compass to Richard, who years later gives the compass to Locke, who goes back in time and gives the compass to Richard, etc. Everything is happening as a result of things that have already happened.
A. Locke gets on the plane and crashes on the Island
B. Locke eventually meets both Richard and Widmore in the past, revealing to them both that he will eventually crash on the Island
C. Time passes--Richard and Widmore proceed to manipulate events in Locke's life, ensuring that...
A. Locke gets on the plane and crashes on the Island
It's all inevitable and impossible to change.
I am reminded of the scene in The Matrix:
Oracle: I'd ask you to sit down, but, you're not going to anyway. And don't worry about the vase.
Neo: What vase?
[Neo turns to look for a vase, and as he does, he knocks over a vase of flowers, which shatters on the floor]
Oracle: That vase.
Neo: I'm sorry...
Oracle: I said don't worry about it. I'll get one of my kids to fix it.
Neo: How did you know?
Oracle: Ohh, what's really going to bake your noodle later on is, would you still have broken it if I hadn't said anything?
The 815ers back in the 70's, in their attempts to change the future, will only cause the events to unfold exactly as the timeline dictates. Example--Sawyer intervenes in the execution of Amy (foolishly risking a potentially huge change in the history of the island) but all he does is guarantee the birth of Ethan, as was fated all along. It really screws with the idea of cause and effect and free will and destiny.
If Sayid does something drastic to Ben in an attempt to interfere with the timeline and prevent his actions in the future, then it will inevitably and ironically lead to his somehow getting involved with the Others and growing up to be exactly the person that Sayid despises. So let's say that Sayid hurts/traumatizes Ben because he grows up to be a jerk, only ensuring that Ben inevitably grows up to be a jerk because Sayid traumatized him.
Cause and effect are going around in a circle...