How I made my facebook almost completely fitna-free:
a)changed my name so that random people could not friend me that I did not want to be friends with
b)deleted all the people I didnt talk to,
c) deleted all the girls, including sisters, except for a few exceptions, here and there, (no more than 5 alltogether)
e) removed all pictures of myself from fb
f) later on I removed all sisters except for relatives
Except for the ads on the side, alhamdulillah, I can say that I have a peace of mind with my facebook!
disclaimer: This is what worked for me. I used to delete my facebook and then reactivate it, but these changes made things much easier. Albeit, facebook can still become a waste of time. It is good when used for Da'wah purpose, and for learning Ahadith posted by beneficial groups and Brothers
May Allah accept from us all and make of the inheritors of the highest level of Paradise. Ameen.