If your social media feeds haven’t been clogged with videos of the ALS Ice Bucket Challenge this week, then you’re in the minority.

The campaign involves people dumping buckets of ice water on themselves (or being doused by others), sharing a video of the experience and nominating others to give it a try as a way to build awareness of amyotrophic lateral sclerosis (ALS.) Otherwise known as “Lou Gehrig’s Disease,” ALS is a progressive disease that causes nerve cells to deteriorate and eventually leads to total paralysis and death.

With its combination of emotion, challenge and social currency, the campaign has become something of a marketing phenomenon, Wharton marketing professor Jonah Berger said in an interview on the Knowledge at Wharton show on Wharton Business Radio on SiriusXM channel 111.  The challenge has been passed among neighbors, friends and relatives, but also to celebrities including Mark Zuckerberg, Bill Gates, Michael Jordan, Anna Wintour and Ben Affleck. Millions of videos have been shared on Facebook, YouTube and other social networks.

“People don’t want to be left out. Anytime you’re at a cocktail party and someone is talking about something, whether it’s a brand or a new band, … you don’t want to be the only person in the group who has no idea what they’re talking about,” noted Berger, who studies word-of-mouth and why things go viral. 

“It’s almost like a duel: You’re calling out a friend of yours and it’s very hard for the friend to say no. It’s a signal of who they are so they want to step up to the challenge…. It’s almost the best type of chain letter in that respect.” –Jonah Berger

Secondly, the ice bucket challenge benefits a worthy cause, “so it’s hard to say no,” Berger said. “It makes you look good to be part of this movement. There is also the challenge aspect of it…. It’s almost like a duel: You’re calling out a friend of yours and it’s very hard for the friend to say no. It’s a signal of who they are so they want to step up to the challenge…. It’s almost the best type of chain letter in that respect.” 

The challenge has led to some backlash, with some people questioning how many who doused themselves actually donated money or have taken the time to understand the disease. Others have said the ice bucket campaign has obscured the needs of other worthy causes and some critics note that it is a waste of water. It’s also led to at least one parody — a trending hashtag on Twitter on Thursday was #PayMyTuitionChallenge in which users “nominated” various celebrities to finance their college education. 

The ice bucket challenge has raised $53.3 million in donations for the ALS Association since July 29, compared with $2.1 million at this time last year, according to Tony Heyl, director of communications and public policy for the Philadelphia chapter of the group. Heyl appeared on the Sirius show with Berger. More than one million new donors have contributed to that total.

“I’m sure there are people who are doing this, and they’re doing it not because of ALS but they’re it doing it because of friends, but that’s a minority.” –Tony Heyl

Berger noted that it’s probably true that some of the people who have taken the challenge don’t know a lot about ALS. “Ideally, you would love everybody who finds out about this challenge to become more aware of the disease, not just donate, not just take part in the easy aspect of it,” he said. “That said, if you are increasing donations and if at least some portion of the people who take this challenge become more aware of this disease, I think it’s good for the ALS Association at the end of the day.” 

Before being tied to ALS, the ice bucket challenge made other appearances in the Internet and even on the Today show when host Matt Lauer was doused in July. Then Pete Frates, a former college baseball player who is living with ALS, learned about the challenge from a friend. Frates recorded his own video (since “ice water and ALS are a bad mix,” Frates bobbed his head to the rap “Ice Ice Baby” instead) and encouraged others to do it in the name of raising awareness of the disease. 

Heyl, who has had friends and neighbors donate money out of the blue since the challenge started to spread, said he’s not worried about the backlash. “I’m sure there are people who are doing this, and they’re doing it not because of ALS but they’re it doing it because of friends, but that’s a minority,” he noted. “If there are some people that are taking advantage of that, but in addition to that, the cause has raised $41 million, then I don’t care that they did that. I care that the cause is making a difference to our families.”