My thing with F-list is that if I haven't spoken to them in a long time, I let them go and delete them off the list. Sounds cold, I know, but there's no real point to keeping them there if I hardly talk to them at all.

Second, with my blacklist I'll usually put people on there that have pissed me off, just like anybody else. Usually flamers, or plain fools who cost the party dearly. After I chill out for a bit, I eventually take them off my blist. Ya never know if they've decided to turn over a new leaf, or have cleaned up their skills.