Since quite some time, I was talking about the changes in the Threat Landscape. I am pretty convinced that the probablity of having something like Blaster or Slammer again is decreasing. This is the good news. The bad news is that threats like targeted attacks are on the raise.
There is a pretty good article covering this: http://www.securitypronews.com/news/securitynews/spn-45-20060911EvolutionoftheHackerThreat.html