As said in this episodes summary:
Walt disagrees, and brings up Victor. Maybe, he surmises, Gus didn't just kill Victor to send a message. "Victor trying to cook that batch on his own, taking liberties that weren’t his to take?" Walt says. "Maybe he flew too close to the sun; got his throat cut." Jesse watches Walt walk away, thinking about exactly what that means for their fledgling new enterprise.
Lately I rewatched the entire series, and now I'm up to S05E03... I know the expressing "flying too close to the sun", but I have no clue what Walt meant to say by that.
It seems I'm missing an important point here... someone cares to explain what Walt means?