i don't know how the algorithm arranges this friends but I just find out the the purpose of the Orderedfriendslistinitialdata.
This list that everyone is talking about it's just for reference. You can see it not only from the source code, but also if you follow these steps.
1. Open your Facebook and turn off the chat, reload the page.
2. Right-click and select source page or view source.
3. Find the list with the ID number of your friend's profile.
4. In another tab or window, open Facebook. Drag the chat list on the side bar until only one friend is showing. That's the first friend on your ordered friends list on the source code.
5. Drag the chat list just enough to see another friend on the list. The new friend that was added is the second friend on the source code.
You can keep going and the new friend that it's added to the list it's the next one in the ordered friends list. As you can see, they are not ordered alphabetically.
Unfortunately, this doesn't solve our question of how the list is ordered but at least we know what it's used for. My guess it's that once you turn on the chat, the list it's merged with the online friends and gives you a more accurate list of people to talk to.