The unfortunate reality is that there will always be people that have no idea what they are getting themselves into by attempting a hot desert hike. The book "Over the Edge: Death in Grand Canyon" is a great source for illustrating the factors for heat-related fatalities. Of course, Grand Canyon is a remarkably different beast compared to a desert peak like Camelback, but a lot of the factors leading to a heat-related death are similar. Like most deaths related to risky behavior, males are more likely to be victims simply out of machismo, and young fit males in their teens and early 20s are prone to suffer heat exhaustion as their young bodies are able to perform at a superior level remarkably close to the point of their core temperature sky rocketing. Middle-age and elderly men are show a higher rate of heat-related hiking deaths due to potential cardiovascular health issues combining with heat exhaustion.
However, all heat related deaths can be attributed to poor decision making or ignorance of the serious nature of summer desert hiking. Most victims of Grand Canyon heat exhaustion are either unaware of how hot the Inner Canyon can be (due to milder temperatures experienced at the rim), or drastically overestimate their body's ability to perform in such heat. I don't have the book with me so I have to recall from memory, but "Over the Edge" states that an adult male hiking in typical summer desert temperatures of 100+ degrees will sweat out something like 3-4 liters of water per hour. Even persons on this website that hike in the desert heat every day would likely be appalled to hear such as statistic. Not bringing enough water for a planned hike is obviously a problem (stated by others in this thread), and can be a deadly mistake, but often this mistake is combined with poor planning in terms of when to hike. Most Grand Canyon heat victims made the mistake of starting their hikes in the middle parts of the day when temperatures were highest and sun exposure was most direct. While some people may suffer heat exhaustion in part due to overall poor physical shape adding time to their hike an d increasing sun exposure, many victims are people of good or even immaculate physical fitness that simply do not gather all the important facts and adjust their plans accordingly.
I think that prevention efforts in order to educate people only go so far, for hiking in the heat or anything else. Some people are stubborn and nothing can be done to stop them from doing what they are going to do. I do believe in putting more rangers on the trails to convince folks to alter their plans if they are unprepared or simply doing something downright stupid. It's a lot easier to get through to people once they are out in the heat of the hike that what they are doing is dangerous, but before it's experienced firsthand, a gung-ho attitude is usually hard to break.
One thing I did notice at the Phoenix parks, was a lack of signage warning of the dangers of summer. The information was often small print buried mong other info on a large sign, while the most prominent signs containing large print tended to make statements about hikers locking and securing vehicles before heading out. I would like to see more prominent warnings at the Phoenix parks about heat danger, and was able to personally notify a representative of the Phoenix parks as such earlier this year at a meeting I attended concerning hiking safety in the Valley. Prominent signage can not be relied upon to change the minds of every potential heat victim, but it's definitely a factor that is neglected in the Phoenix parks that, if done properly, may actually save a life or two.