I don't post with filters. A few posts are friends-locked, but if you can see those then you can see everything. No one has (so far) complained that I post too many things about X and asked to be filtered out, and the idea of deliberately hiding things from people doesn't really appeal to me (and also I don't like it much when I find a post I've been filtered out of so it would feel wrong if I started doing it). Anyway, this means (or perhaps is a consequence of the fact that) I don't bitch behind people's backs much. OK, except occasionally about people from my real life who are not on LiveJournal, though that seems different somehow (he said, hypocritically).
So the following hypothetical question occurred to me:
If I should have a sudden urge to bitch about someone who is on my Friends list then I should…
Button it (i.e. not post)
Post it openly and live with the ensuing drama
Post it privately (i.e. visible to no one) and get it out of my system
Just make the filter already
Wait until I know they're not at a computer, then post it. Before they get back, delete it or make it private.
Choose another option not listed above
(It was the thought of #5 that made me post. <evil grin>)