- Cameras may have caused the Hawthorne effect: https://en.wikipedia.org/wiki/Hawthorne_effect
- The article (the news one, haven't read the original yet) talks about the increase of probability that some bystander will act, with increase in group size. The bystander effect study talks about the decrease of probability that a particular individual will act, with decrease in group size. These two things may very well both be true and there may be some non-linear effect at play (i.e. after a certain group size, the increase in the probability of someone acting wins out over the decrease in any one person acting.