An awful lot of game studios and publishers these days seem to view free-to-play as the holy grail, but finding the sweet spot between giving the store away and taking unfair advantage of your players is a tricky business. League of Legends is one of the few games that really seems to have nailed it, and yet Ubisoft Blue Byte's Teut Weidemann says it's not a game that other publishers should emulate.

The problem, in Weidemann's eyes, is that Riot Games is just too darn generous with its players. Looking at the numbers from 2009 to 2013, he calculated that League of Legends has a conversion rate—that is, the portion of people who actually pay to play—of just 3.75 percent.

"Usually, conversion rates for client-based games is between 15 and 25 percent," Weidemann told Gamasutra . " World of Tanks has 30 percent. It could afford to have one-third of the customer base and have the same amount of money as League of Legends."

And why does a game as popular as League of Legends have such a low conversion rate? Therein lies the bit that gamers will likely take issue with: According to Weidemann, Riot isn't trying hard enough to actually make money from the game.

"Riot doesn't care. Optimizing monetization is not the top priority," he said. "They monetize purely through their reach. So it only works because of the large user base, and if you don't have that user base or don't expect to, you should not adopt their monetization. It should not be a role model for your monetization system."

In Weidemann's defense, he's coming at the issue strictly from a business perspective, which doesn't always run perfectly parallel with "keeping gamers really happy," and ultimately it's less a criticism of League of Legends than a warning to other studios that they likely won't be able to duplicate its formula for success. But it's interesting that while he he exhorts others to "learn why it works, and where the mistakes are, and why they can afford to let the conversion rate be so low," he never touches on the possibility that Riot is successful precisely because it doesn't focus on monetization. Maybe there's a good reason for that; but maybe it's one of those ideas that just crazy enough to work, too.