What is the motivation for Virus Writers?

From: Trevor (sales_at_logicians.com)
Date: 12/14/03 

Date: 14 Dec 2003 08:00:47 -0800

I have just finished paying to get my PC cleaned after the W32 Blaster
Worm infected it.

I am wondering why people write viruses at all. What is the motive?

I heard it is an intellectual challenge trying to break systems. But
what is the challenge in hurting a home PC, or someone with a small
business? I cannot understand the reason for attacking ordinary people
who are just trying to make a living.

Terrorists attack ordinary people because they are "soft targets" or
easy to kill and hurt. They rarely attack soldiers and police
officers.

If virus writers attack us because we are easy targets, then surely
that defeats the point of the challenge.