What are the differences between bullies and plain old trolls?
Excellent question. First, what is a troll, and how does a troll cross the line to become a bully? The definition is found in many places. The alt.syntax.tactical FAQ is one of the best resources to learn about trolls (and bullies) and how to deal with them. The excellent Anti Troll FAQ describes classic trolls as "old definition" or "irritating" trolls. It then goes on to describe "destructive", "nasty", or "evil and illegal" trolls. These are better described as bullies. Trolling is not their primary purpose for being in your newsgroup. By this FAQ's definition, these are bullies, not trolls. A troll posts something outrageous in a newsgroup in an attempt to gather the maximum number of outraged replies. It is an attention-getting thing. A bully needs to control. Again, check both the excellent FAQs cited.  READ them. Then, read on.

How long does it take to spot a troll?
Usually it takes less than a second. If someone (who is the target of a troll's wrath) posts anything in a newsgroup (especially something helpful), they are on it like a duck on a June bug. If it is hateful and spiteful, you probably have a troll on your hands, and you may well have a bully on your hands. Read on.

So, when does a troll cross the line and become a bully?
When he/she stops merely seeking attention and starts trying to control other people.

The playground bully syndrome
The classical definition of a playground bully describes a person who is a socially inadequate outsider, but more recent studies reveal them to be clever and cunning manipulators who have an above-average ability to see what makes others tick and who use this ability to gain control over others and torment them. They become adept at tuning in the apprehensions and fears upon which to play. They find buttons and push them. When they can make someone respond to them in predictable fashion, they believe that they "own" that person. Remember another aspect of the playground bully. They reign supreme when the other "normal" kids on the playground not only turn a cold shoulder to the bully's victims, but even join in the taunting (for fear they will be the bully's next victim).

What about cyberbullies?
Cyberbullies are serial bullies who use the Internet (or in this case, Usenet) as their playground for bullying and controlling others. The characteristics of a serial bully are found at Bullyonline.org. All you have to do is read a few lines to see what our Usenet bullies are all about.

It's about hate.
The bullies seem to need an enemy to hate. I suppose it's necessary to have a scapegoat for their lack of any real purpose on Usenet. So they pick on anyone who is highly visible in a newsgroup, and they start attacking. Their attacks need not be based on any truth. Any trumped up accusation will do. Then they repeat their attacks, again and again and again.