The 16-year-old Toronto native trumpeted the release of "Handwritten" with a "#HandwrittenBuyouts" Twitter contest, urging his swooning fans to purchase every last Mendes CD from store shelves.
On Tuesday afternoon, he tweeted to his nearly three million followers: "Go to stores today & buy all the album copies ! U can find a #GoldenShawnAccessPass & meet me ! #HandwrittenBuyouts."
Attached to the tweet was a polished image (also posted to Facebook) repeating the instructions and touting a grand prize for two to meet Mendes and watch him perform in a warm-weather destination. Other prizes include meet-and-greet access and merchandise.
And judging by replies to the tweet — which was retweeted more than 7,000 times and got more than 12,000 favourites — fans of the Vine sensation were eagerly heeding his command.
One devotee tweeted a photo of herself clutching a colourful wad of Canadian bills with the message: "I guess all my babysitting payed (sic) off! :)"
Another female fan from Ontario tweeted a photo of 16 copies of the album strewn across her bed — along with a picture of the total bill: $255.38.
Multiple child advocacy organizations raised questions about the strategy on Wednesday.
"I think that's really concerning, considering his appeal to younger fans," said Campaign for a Commercial-Free Childhood associate director Josh Golin, who called the campaign "unethical."
"Younger fans are unlikely to understand the odds of contests — and that their chances of winning any type of contest are astronomically against them. And then to encourage kids to buy multiple copies when there's no use for multiple copies is particularly exploitive."
Following Mendes's tweet, pictures began rolling in from fans dutifully bingeing on the earnest "Life of the Party" guitarist's full-length debut.
Mendes himself retweeted photos of fans showcasing their "Handwritten" hauls in multiple ways: fanned out in their fingers like a poker hand; spread about the front seat of the car; or stacked, neatly, 20 discs high.
"The harm could be that kids are going to be spending money that they don't really have — money they might need for other things — (and) that you're taking advantage of people who don't necessarily have the critical-thinking skills yet to be able to make good decisions about managing their money," said Matthew Johnson, director of education for Ottawa-based Media Smarts.
"When your audience is fairly young, obviously you do want to reach them, but you could definitely make an argument that it's irresponsible to be encouraging young people to buy multiple copies (of an album)."
Most of the fans pictured tended to be adolescent or pre-teen girls. Although some seemed to be alongside their parents, Johnson points out that social media allows advertisers to reach children without as much parental oversight as other platforms.
"When your kids are watching a commercial on TV, there's a reasonable chance you might be sitting next to them or walk into the room," Johnson said.
"(You) help your kids understand how a commercial might be misleading, or understand how it might be playing on their emotions.
"But because these messages are being delivered in a context where it's probably only the child who's going to see it ... parents don't really have that opportunity."
Added Golin: "I imagine most parents would be shocked to know their kids are being urged to clean out a store of an album."
Further, child advocates point out that kids of a certain age have an innocent view of social media.
To some younger fans, Mendes's missives aren't coming from a marketer — they're coming from a friend.
"(Kids) are being manipulated, really," said Sierra Filucci, executive editor of parenting content for Common Sense Media, a San Francisco non-profit that helps kids "thrive in a world of media."
"They're feeling like they have a personal connection to this artist, who's adorable and really compelling, and they feel like they're doing something specifically for him.
"But they don't realize they're actually part of a marketing campaign designed to attract their attention and take their money."
Universal Music Canada didn't respond to a request for comment.
Follow @CP_Patch on Twitter.Suggest a correction