I don't understand all the negativity. This has clearly been a very successful campaign so far.
Does everyone who did the challenge actually know what they're doing it for? No, but that's not the point. If that person tags 3 individuals and 1 of them actually bothers looking up what ALS is and perhaps make a donation, then it was a win. Donations have clearly been spiking so there's no arguing with that.
The "challenge" itself is very well thought out. It's easy enough to do, pretty safe, but at the same time can be mildly entertaining. Because it is so easy to do, setting the time limit (24 hours) also makes sure that the momentum is kept going. This is why it's so successful and was able to make it spread so quickly.