The Sasser arrest has been big news, of course. However, there was another, important arrest in Germany on Friday too: a 21-year old unemployed man linked to creating Phatbot / Agobot (or variants) was apprehended too. This was in Loerrach, Germany.
There seems to be no link between this guy and the Sasser author. Regardless of that, both arrests were synchronised to happen on Friday at 14:00 local time.
As reported here before, the source code of Phatbot has been floating around in the underground, so this arrest probably won't directly stop the flow of new variants. Indirectly it might have an effect, though. Hopefully the pressures among the virus writers are growing.