Not surprising, when you think about it.
First there are obvious anomalies, such as the police taking such a long time to get to the island where the massacre took place.
Then there is also the possibility/probability of people manufacturing "evidence" that would imply conspiracy and disseminating it on the internet.
People saying Breivik has different coloured eyes, people saying there was more than one shooter, people saying that both the entire operation and the downtown bomb were too complex for a lone operative and so forth.
So let the theories rain down from cyberspace. The possible motives and conspirators out there would boggle the mind!