One of the interesting things about consumer electronics is that the defaults tend to always be very obvious and well known. So all alarm clocks go off at 12 AM (much to Joel's disappointment), people's hard drives are open for the viewing (because the web server is on on their desktop machines, directory browsing is on and firewalls are off (or missing)), and apparently, one of the most common first pictures for new cameras are boobies. The only flaw with this analysis is that it doesn't look at what the next 100 pictures are either... I'd suspect it's pretty close to what the first one is. Actually, I'd be that as number of pictures per camera increase, likelihood of pornography also increases, considering pornographers just happen to take so many pictures.
