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There are two things that are certain about cryptocurrencies: Lots of people are talking about them right now, and lots of people don't really understand them.

In the meantime, Facebook is banning cryptocurrency advertising on its social network. The company announced the new policy on Tuesday, which includes barring ads for bitcoin and initial coin offerings, or ICOs.

The reason is ads for those things are "frequently associated with misleading or deceptive promotional practices," Rob Leathern, product management director for Facebook ads, said in a blog post. He added that many companies advertising cryptocurrencies "are not currently operating in good faith."

The ban isn't permanent. Leathern said the policy is "intentionally broad" while Facebook figures out how to better detect deceptive and misleading ads and ramps up enforcement. "We will revisit this policy and how we enforce it as our signals improve," he said.

The new policy not only applies to Facebook, but its other platforms, including Instagram and its Audience Network, where the company places ads on third-party websites.

Meanwhile, there's been a lot of buzz around Facebook and cryptocurrency. CEO Mark Zuckerberg name-checked it in a post detailing his annual challenge for the year -- a broad strokes announcement on how he'd fix some of Facebook's biggest issues, like misinformation and harassment.

Regarding cryptocurrency, he said he's interested in that kind of technology. "But they come with the risk of being harder to control," he wrote. "I'm interested to go deeper and study the positive and negative aspects of these technologies, and how best to use them in our services."

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