"The study, carried out for the Department for Transport, found that in 2% of cases where cyclists were seriously injured in collisions with other road users police said that the rider disobeying a stop sign or traffic light was a likely contributing factor. Wearing dark clothing at night was seen as a potential cause in about 2.5% of cases, and failure to use lights was mentioned 2% of the time."
This is from
http://www.guardian.co.uk/lifeandstyle/2009/dec/15/cycling-bike-accidents-study. There is a link to the study.
That seems to me to show that no lights is not as serious a problem as you might think.
Perhaps I should make it clear I make sure to have good lighting, and cyclists with no lights piss me off too.