Hehe, no of course it was all about the photo and the retrogadely injected task Faraday gave to Desmond. The photo is the reason he started believing history can be altered.

I just watched Eloise apologizing to Penelope after Ben shot him. She said "For the very first time since long time I don't know what is going to happen". Faraday altered the future when he spoke to "his constant" and the dharma photo was possible proof that he succeeded. Desmond originally would not have been in LA and wouldn't have been shot. Faraday proved history can be altered and thus there was no H-bomb core originally.

Which, to conclude, brings me back to Faraday seriously meaning what he tells Jack, to stop the chain of events starting with the incident leading to the crash of 815, Widmore's boat.

Leaves the question where Faraday found out about the "chain of events" if he knew nothing about the island before he went brainfried and didn't get better before he got "healed" by arriving on the island. How did he do it?