The 2007 Estonia cyber attacks are some of the most widely reported and studied cyber attacks. Yet to date, no definitive conclusion can be made concerning the motive or exactly who sponsored the attacks. The article quotes various authorities who have widely varying theories of the motives behind the Estonia attacks. This is an excellent example of the difficulty in determining motive - or conversely, the ease in mis-identifying an attacker's motive.
"The difference between government-sponsored attacks and grassroots cyber terrorism is growing increasingly fuzzy, even as researchers try to sift through who did what on Estonia's Web. And the difficulty of tracing responsibility for even massive cyber attacks suggests that such maneuvers may become an effective tool not just for indiscriminate vandalism, but also for stealthy cyber censorship."
When Cyber Terrorism Becomes State Censorship