Bitcoin and cryptocurrency prices have struggled this week with the crypto market's combined value slipping under $1.5 trillion—down from $2.5 trillion in May.

The bitcoin price, after getting an unexpected boost from Tesla billionaire Elon Musk last weekend, has resumed its decline over the last few days, falling back toward $30,000 per bitcoin.

Now, as bitcoin charts show the price 50-day moving average has fallen below the 200-day moving average—a pattern known as the "death cross"—Coinbase cofounder Fred Ehrsam has warned "most" cryptocurrencies and crypto-assets "won't work" and "90% of NFTs" will have "little to no value in three to five years."

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The bitcoin price has lost almost half its value after hitting a peak of around $65,000 per bitcoin ... [+] in April.

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Bitcoin's "death cross," despite its ominous name, appears to be a lagging price indicator. The last time the trading pattern occurred in March 2020, it heralded a huge bitcoin bull run that helped even smaller cryptocurrencies surge to all-time highs.

"People are going to try all sorts of things," Ehrsam, who has gone on to found the blockchain investment firm Paradigm since leaving Coinbase in 2017, told Bloomberg this week, warning many of those smaller cryptocurrencies won't survive. "There'll be millions and millions of cryptocurrencies and crypto-assets, just like there were millions and millions of websites. Most of them won't work."