I don't think you can masturbate too much unless you are causing physical damage or pain, or your habit keeps you from doing other important things or socializing. For example, if you skip work to masturbate all day, that's probably a sign of a problem. Same if you are out with friends and leave so that you can go home and masturbate.
I do think porn can be harmful, especially excessive porn. And the more unrealistic the porn is, the more harmful it can be, too a point. I think that a NoPorn movement would have more positive effects for the participants than NoFap.
I think masturbation can be addictive and so can porn. It's very hard to compare addictions to these things with things like nicotine, heroin, alcoholism, because they don't have the very apparent downsides, people don't die from a porn overdoses. That doesn't mean that the addiction is any less strong. I have at times been addicted to nicotine and alcohol which are supposedly the most difficult addictions to break. I have quit both of these things, and find it much more difficult, at times, to stop masturbating, and I don't believe its something I could ever stop completely.
Supposedly ejaculating 30 times a month of more is good for prostate health, but there are a lot of factors that could effect that and I hear that statistic a lot without hearing the actual methods behind determining it. I think its a statistic that is amusing and obviously leaves some room for jokes, so guys are happy to propagate the results of the study. I don't know if they considered things like age, history of cancer, behaviors that are linked to cancer like smoking. And like Twoton said, if there is a real need to ejaculate it the body will regulate that, either through nocturnal emissions or through the strength of the urge. 30 seems like an arbitrary number, but I do my part to try and keep myself close to that rate.