Facebook has stopped allowing its users to mention the name of another social network on its apps and website, but it's not for the reason you might think.

The site is Tsu.co, an invite-only social network that is premised on the idea of sharing ad revenue with its users. The problem, it seems, is the site became a huge source of spam on Facebook so the company blocked its users from mentioning the URL.

Typing Tsu.co, anywhere in Facebook, Instagram or Facebook Messenger results in various error messages that let you know your comment won't be posted. (There doesn't seem to be a similar ban on WhatsApp, though.)

The problem, apparently, is Tsu's business model, which is premised on financially rewarding its users based on how much they share. Tsu keeps 10% of ad revenue generated by users' content, with the remaining 90% distributed among the users who invited that friend. If that model sounds familiar, it's because it's a lot like how pyramid schemes work.

Tsu's business model. Image: Tsu

Facebook says sites like Tsu encourage "spammy behavior," which violates its rules for developers.

“We require all websites and apps that integrate with Facebook to follow our Platform Policy," a Facebook spokesperson told Mashable. "We do not allow developers to incentivize content sharing on our platform because it encourages spammy sharing and creates a bad experience for people on Facebook.”

Notably, the company's Facebook Page, which has more than 11,000 fans, is up and running (URLs posted there link back the page itself, rather than the company website).

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