What just happened? After being stuck below $4,000 for most of this year, Bitcoin's value has skyrocketed over the last few weeks, helped in no small part by Facebook's announcement of its Libra virtual currency. But one person not convinced by the crypto resurgence is Donald Trump, who says he is "not a fan" because their "value is highly volatile and based on thin air."

The president posted a series of tweets yesterday criticizing Bitcoin and other cryptocurrencies. He singled out Facebook's upcoming Libra virtual currency, which he says, "will have little standing or dependability."

Trump added that "if Facebook and other companies want to become a bank, they must seek a new Banking Charter and become subject to all Banking Regulations, just like other Banks, both National and International."

Like Bill Gates and Berkshire Hathaway CEO Warren Buffett, Trump is a cryptocurrency skeptic, warning that unregulated crypto can facilitate illegal activities such as drug dealing. He finished the tirade by reaffirming his confidence in the US dollar. "We have only one real currency in the USA, and it is stronger than ever, both dependable and reliable. It is by far the most dominant currency anywhere in the World, and it will always stay that way. It is called the United States Dollar," he wrote.

Last month, Facebook revealed that Libra and its Calibra digital wallet would arrive next year, but the Senate Banking Committee was quick to announce that it would be holding a hearing on the virtual currency.

At the beginning of July, the Democratic heads of the House Financial Services Committee asked Facebook to "immediately cease implementation plans" for Libra so regulators can explore concerns including hacking, data security, and global financial security.

In addition to the all the problems it is facing, Libra could be banned in India. This would be especially bad for Facebook as the country makes up a large portion of users the crypto is targeting.