How does Facebook organize chat list?

[Kseniya]

How does Facebook determine who goes on the top of the list and who goes under "More Online Friends"? Sometimes I'll see someone who was under "More Online Friends" randomly switch to the top of the list. Is there any reason for that?

Thanks.
Sometimes it happens with people who I've never chatted with or interacted in any way on Facebook.

[abraXus]

it's based on who you interact with the most

[Karen]

It depends on the organized friends list of yours. Like you have friends list like close friends, acquaintances, etc and others friends of yours who are not added into any list will show up in the more online friends.