As a follow on, runway 25L is the longest runway at LAX at 12091 ft long. Don't know about the departure you saw but at times performance requirements dictate its use even if it heads you in the wrong direction initially. Lax doesn't like to cross departures from the 24 and 25 complexes. If you depart the northern runways(24's) you generally go straight out or make a right turn twords the north. If you depart the south runways (25's) you generally make a turn to the south. This is true even if its completely away from your destination. They usually have you headed in the general direction you want within a few minutes by the means others have described here.