My DD15 had this explanation:
When Daniel met Desmond on the island he didn't recognize him, because he hadn't met him in the past YET. Same with Danielle. When she met Jin on the island in the present, the thing in the past hadn't been changed yet.
No, that would screw up the laws of time travel. Basically if something is going to happen it already it has. That's why the jumping losties can't interract with the past.
Desmond's situation was explained when he told us that he didn't remember the encounter until the dream. Therefore he wouldn't have recognized Daniel.
And Danielle is crazy, and now we know why and just how much. Jin shows up at the most tramatic moment of her life. She's totally freaked out and think he's "sick" too. She has seen crazy things she can't explain, but doesn't tell the losties everything. I'm sure she has seen plenty of "dead" people or things that don't belong and just shrugs them off by now...
I posted this on the other thread, but thought you might have some interesting thoughts too...
I thought one interesting part was at the beach with Jin and Danielle. When Jin came across the corpses I said, "Wow, they could be twins, I don't remember twins on the boat." lol Then when we saw "Robert" and Danielle I realized the smoke monster was sending out flesh and blood replicas of Robert?! And Danielle had already killed two? No wonder she's nuts and doesn't remember Jin...
I think it's interesting that the island can do this and it's been confirmed, so all of the "dead" people we saw come back and talk to the Losties weren't just in their imaginations or hullucinations, they were "real"?
And one more thing, we know that Daniel has 2 more very important jumps,
1. To see child-Charlotte
2. To go into the being built Orchid station...
So I guess John doesn't completly fix things...maybe he just makes it happen less frequently?