Internet Fuckwad Theory
The Greater Internet Fuckwad Theory, first articulated by webcomic artist John Gabriel as shown above, states that a normal person provided with anonymity and an audience may undergo a negative personality change. In other words, anyone using the internets becomes an asshole.
Using the Theory
The general rule of trolling is that the more moronic a user is, the easier they will be to troll. This is only partly true. There are often cases where the other user is so terrifically and utterly retarded that they become difficult to make fun of.
Note: Many of the groups listed in the diagram overlap - thus there are many youtubes who happen to be furries and PETAfags lurking on deviantArt.