Until yesterday, if you were to browse the video pages of popular gaming YouTubers Trevor "TmarTn" Martin and Tom "Syndicate" Cassell, you'd have found a string of videos about the Counter-Strike: Global Offensive gambling site CSGO Lotto. These videos showed the pair gambling weapon skins on the site, which allows anyone over 13 years of age to trade their hard-earned weapon skins for actual money. They often won big, resulting in videos with titles like "HOW TO WIN $13,000 IN 5 MINUTES."

Ordinarily, such a video might be regarded as the soft of clickbait you'd see on a banner ad while browsing unscrupulous websites. But, with millions of subscribers, both Martin and Cassell have a captive audience to watch their videos. And now this audience has been turning out in droves to launch allegations of unethical behaviour and lack of disclosure against the two YouTubers.

It turns out the owners of the CSGO Lotto website are none other than Martin and Cassell.

The pair have since made their CSGO Lotto videos private, but the damage has already been done. Martin and Cassell have promoted numerous CSGO Lotto giveaways and made videos showing how players could win cash on the site. Despite serving as owners and vice-presidents of CSGO Lotto since December 2015, at no point in any video did the pair disclose those connections, instead claiming that CSGO Lotto simply sponsored their videos. Martin has promised to issue an official statement about the controversy later today.

In the meantime, he has taken to Twitter and YouTube in an attempt address some of the issues.

"I've admitted to wishing I was more upfront about owning the site," reads a now deleted post. "It was always public info but I was never very outspoken about it. My idea was to keep business business, while the focus of YouTube was simply making entertaining content. Obviously that was misleading to viewers and something I very much regret. I've never been perfect and I 100% own up to that mistake. That being said, everything we've done up until this point has been legal, that has been a #1 priority of ours. The day it becomes illegal is the day we cease activity."

Unfortunately for Martin, research undertaken by h3h3Productions and PCGamer has found no evidence of his interest in CSGO Lotto being declared anywhere. A vague statement (found via the Wayback Machine) saying "Video made possible by CSGO Lotto" was added to some videos after they were uploaded. Even worse for Martin is a transcript from another video, which reads:

"We found this new site called CSGO Lotto—so I'll link it down in the description if you guys want to check it out. We were betting on it today and I won a pot of like $69 or something like that, so it was a pretty small pot, but it was like the coolest feeling ever. I ended up following them [CSGO Lotto] on Twitter and stuff, and they hit me up and they're talking to me about potentially doing like a skin sponsorship..."

Other prominent YouTubers have since been dragged into the controversy. Josh "JoshOG" Beaver has admitted to owning equity in CSGO Lotto, while also failing to disclose his "sponsorship." He has now begun removing videos that reference CSGO Lotto. Another YouTuber, PsiSyndicate, admitted that several of his own CS:GO weapon skin videos were rigged and created in association with another CS:GO betting site called SteamLoto. He claims that he was approached by the site, which provided him with valuable weapon skins to "randomly" unbox. He then acted as if they were random wins.

For a brief period, users clicking through to the CSGO Lotto from Steam were shown a warning that the site may engage in phishing, scamming, spamming, or delivering malware. However, Valve has since removed the warning.

This isn't the first time that YouTubers—and Cassell in particular—have been in trouble over a lack of disclosure. Last year Cassell was found to have been promoting multiplayer horror game Dead Realm on his channel without declaring his financial ties to the game's publisher 3BlackDot, which was founded with the help of Cassell and other video-makers a year earlier. Meanwhile, a number of YouTubers have faced criticism after it was discovered that the company Mondelēz had paid them to promote Oreo biscuits in "Oreo Lick Race" videos. Few participants disclosed the deal.

At the time, the UK's Advertising Standards Authority (ASA) ruled that it "pays to be honest," before banning the campaign.

"It is perfectly legitimate for vloggers (or bloggers, tweeters) to enter into a commercial relationship and be paid to promote a product, service or brand," the ASA noted at the time. "But when that commercial relationship is in place then the onus is on the advertiser, and by extension the vlogger, to be upfront about it and clearly disclose the fact that they’re advertising. We're going to be communicating clearly to advertisers the outcome of this ruling and raising awareness amongst vloggers of the need to disclose when the content of their blogs is paid for."

Aside from the lack of disclosure on YouTube—which would clearly violate the ASA's guidelines—both Cassell and Martin could face criticism over founding CSGO Lotto in the first place. A recent report from Bloomberg claimed virtual weapons were turning gamers as young as 13 into serious gamblers, and that the betting boom generated as much as $2.3 billion (£1.75B) last year. Meanwhile, a lawsuit filed in June by CS:GO player Michael John McLoed alleges that Valve allowed an illegal online gambling market to develop.

"In the e-sports gambling economy, skins are like casino chips that have monetary value outside the game itself because of the ability to convert them directly into cash," the suit reads. "In sum, Valve owns the league, sells the casino chips, and receives a piece of the casino's income stream through foreign websites in order to maintain the charade that Valve is not promoting and profiting from online gambling, like a modern-day Captain Renault from Casablanca. That most of the people in the CS:GO gambling economy are teenagers and under 21 makes Valve’s and the other defendants' actions even more unconscionable."

Regardless of the outcome of the lawsuit, it's extremely likely that the controversy surrounding Martin and Cassell will escalate beyond the relative safety of YouTube. And when it does, expect a whole lot more YouTubers to come forward with undisclosed deals.