I've been trying to form some opinions on this for a while. It seems a complicated issue to talk about, for reasons that I wasn't quite sure of. I believe I figured out why people are annoyed to have an adult conversation about it, so I will say a few words.
I don't mind that people are suddenly giving money to this as a cause. I would think other causes will be trying to adapt it and will catch up. They will learn how to make viral and invasive messages about their own serious matters too. This was just one of the first to make it that way in the internet age (Susan Komen and others with the colored ribbons would be one of the first to make it that way in the pre-internet age).
I'm a little disturbed that it is inefficient. The utilitarian calculator in me is really annoyed that there are dozens of other things that would be less wasteful as a display of viral contests. Dumping clean water and ice on your head is a pretty obvious "first world" thing to do, and screams "look at me!", I care about X and will do something silly to prove it. That's a little irritating but not so much so that I find it necessary to object to it out of hand. It feels more like an itch brought on by extroverts and their need for attention and overt displays than actual narcissism.
There are also causes more likely to produce a considerable net positive social and global good by giving to them (malaria research, basic genetic research, clean water, or general cash donations to the poor). I think this is the general feeling of a lot of people who are mildly annoyed by this "contest" or challenge or whatever is an offense against other causes is being caused. And it is true that some, perhaps even most of the money is exclusive rather than freshly produced charity. Meaning that some other very worthy causes won't be getting as much money for research of cures or prevention or treatment of the sick, the infirm, or the otherwise at risk.
That point of view however has been expressed rather poorly and reacted to with enormous vitriol. As though anyone who says it is a) completely unaware and unconcerned of the suffering imposed by ALS or b) doesn't want it to be cured. If I thought these donations would reduce the suffering imposed by leading to a cure or prevention/treatment method, we'd be in some major hot water there. It's possible they will, but not very likely. It's much more likely giving someone in a third world country 100 dollars in start up capital will do something, or a 100 dollars of water or water cleaning research or technology to a town in Central Asia or Africa, etc. So I would rather do that.
I don't know why that PoV complaint should matter. If people, like me, are applying some utilitarian logic and are actually annoyed the money is going to ALS instead of something else conceived of as more productive, give the money to something else, and ask others to do the same. We are not required to obey to give money only to this one thing. This is the part that seems to be missing from commentary on the subject. If dumping ice on each other's heads is the transmission vector, dump ice on your head for some other reason and try to use what's working now for that cause instead. This isn't a legally binding requirement that once challenged, our money is locked into this donation. It's a blank check. Treat it as such.
Charitable giving and "awareness" generally are not inherently bad objects. It is desirable that we should be concerned with the suffering of others, even those unknown to us, and attempt to help them in indirect ways if necessary. We should avoid criticizing people for doing this, which I believe is one reason people are annoyed with anyone saying "eh" at their giving to ALS now is a perception of criticism.
Giving is often an excuse to do wasteful or immodest or even immoral things elsewhere in one's life though. Philanthropy isn't necessarily something corporations or the wealthy do simply to "be good". These actions are reputational adjustments they can point to when people complain about something else they are doing (which may actually be worse). Altruism isn't really a big thing for most of us. It is usually more important to be seen caring about something than to produce an effect on the problem we are proclaiming loudly to care about. This is what I think most pro-life/anti-choice people are doing, as an example, trying to express concern about abortion without working to make it less likely to occur. Because that would be too hard and require listening. This as a cause isn't quite in the same category. It isn't necessarily doing damage to us as a society to loudly express concern in this way about this thing instead of something else of deeper and more significant damage to our own society and well-being (say, the war on drugs, or expanding birth control accessibility, or dealing with miscarriages, or diabetes, and so on down our litany of woes). A few million dollars for this instead of a few other charities isn't a big deal in the scheme of things.
But it's in the same variety of action and could be twisted quickly to something that could be damaging. Which is a little worrisome. One of the biggest problems is that the point many use to justify is "awareness". Awareness is useful if it can be combined with something that we can do to mitigate. Awareness and understanding of depression is, for example, something we can act upon as an individual to be attentive and listen to others, or otherwise be present. Awareness of AIDs is something that allows us to try to prevent it from spreading and afflicting others. Awareness of police brutality or violence allows us to gather together to try to reform our system of oversight so that it might be punished accordingly or at least transparently. Awareness of ALS would be kind of like awareness of an impending alien invasion. There's not a whole lot we can do about it right now and it's been worked on for decades. Maybe these donations will have long term impact. I hope they do and I think most everyone involved hopes they do. They aren't being malicious by giving. But "raising awareness" isn't really a way to deal with a long-term problem like this. The reason is that once people feel "aware" of a problem, and maybe do something like dump ice buckets on their heads, they may feel they have absolved themselves of the responsibility to do much else about it, and passed it on to others to act. They have met their "I care" quota for the day and can let something slide. I have very little "I care" as a quota to go around, so I find that dispensing it in this way is not very effective in actually demonstrating whether I care about something or not. This is a serious problem. It deserves serious attention. It is difficult to do much about it though, so I find it is a better use of time and money and energy to go "care" about something else instead.
I find it curious that other people don't recognize that, but I don't think it is necessary to judge them for this decision. And I think much of the commentary has come off as a judgment that they are doing something wrongful by acting in this way. Which should justly make people mad.