I give Anonymous Coward a -6 modifier. There is no reason to post anonymously on a web board that you dont have to provide tracable information to sign up on unless you are trolling or flaming.
I read slashdot at a threshhold of 1.
Obvious Trolls: The most obvious trolls are those who never respond to a thread, just post "Funny" comments to gain karma points to burn when they go trolling. They are almost always very easy to spot. Most new accounts that post a lot are trolls, so the top 10% gets an automatic -1 modification.
Snotty Foreigners: This is an American web site, run by Americans in America. Non-Americans who post rude and just plain ignorant posts about how such and such post or story is overly US-Centric gets a quick ride to my foe list.
Flamebait: Name-calling is childish and doesn't belong in an adult web board. Yes, I realize not all slashdotters are of an adult age (to say nothing of mentality) but people who post a message for the sole purpose of being a jackass are foes too.:)
People who post comments I find extremely interesting and/or extremely funny and who have a history of posting such quality content in my opinion.
People who do interesting things like write games where you push people off the stairs for points.;)