Multiple PlayStation 3 users are reporting on the official PS forums and on Twitter that theirPSN friends list is disappearing, meaning that no other players will show up in that section of the XMB.
Now, there seems to be some issues with the PlayStation Network, and according to Sony, this should be fixed in the next few hours:
Hi guys,
I can confirm that your friends have not been deleted. There is some minor maintenance ongoing and this has caused a small number of users friends list to not load.
Wait an hour or so, sign in then out and the list should refresh.
Edit* if it does not, please bear with us whilst its fixed.
SFZ
Official Source: http://community.eu.playstation.com/t5/PlayStation-Network-Technical/PS3-Friends-list-gone/td-p/19484930/page/8
http://www.thesixthaxis.com/2013/10/18/psn-users-report-friends-list-disappearing/