A Dutch research (in Dutch) into the second live's of 250 hard core Second Life users shows that 40% of them feel sometimes griefed by other residents of the virtual world. EPN's research is apparently a first of it's kind and it's main focus was on the heavy users to get a better understanding of the impact these kinds of virtual worlds (and interreality as they call it) might have on society once they become more populated by 'the masses'.
Some of the results:
16% of the interviewed ‘residents’ is entrepreneur. 50% of all interviewed said that they make money in SL incidentally. 60% of those are highly educated and of those 60% are female. 50% of the research population is between 25 and 40 years old.
30%+ spends more then 40 hours in SL every week! And further research showed this was a conservative estimate by these users and 40% of the interviewed would consider themselves addicted. But no (typical) negative consequences (related to addicition) were discovered.
There will be a follow-up to this research and Linden Lab's Philip Rosedale has indicated they are interested in participating. When the results of this research were presented he was speaking in Amsterdam at PICNIC '06 in the same session I was speaking (showing a demo of a talking Eccky chatbot in my SL living room...).