Citron Research's Andrew Left is not at all impressed by the latest wave of initial coin offerings (ICOs) and the Grayscale Bitcoin Investment Trust (GBTC) . 

ICOs have become popular as more and more start-up are using them to raise money. 

Citron Research's Left, who is a well known activist short seller, has also bet against Grayscale Bitcoin Investment Trust. He told TheStreet he has "no long-term view on Bitcoin.....more of a comment on that particular vehicle [ICOs]." And that comment is one of skepticism, even though he doesn't dismiss the cryptocurrency at large.

"I would be more bearish on the wave of ICOs than Bitcoin," said Left. 

Recently on CNBC, Left said he has taken a short position on Grayscale Bitcoin Investment Trust, because the net asset value is twice the amount of the underlying Bitcoin.

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"That alone is completely ridiculous," Left said. "But on top of that just go read the SEC filings and you will see they [Grayscale] do not have insurance of the the Bitcoin that they are custodians of."

Left sees this as a negative sign. To boot, the GBTC doesn't offer a guarantee that its owners are going to get a distribution of Bitcoin cash.

Left said he is short and held the position "recently" and refused to discuss the size. However, he added that "I'm half-hedged and half-unhedged."

As a seasoned investor, he's willing to take on some risk as long as he can protect his downside. But he's a realist when it comes to the danger of high valuations that can only reach certain altitude.

"I actually think ... as somebody who has been trading markets for 30 years, I have a certain level of understanding, and that would be the higher things go, the more thin the air becomes," he said. 

The Grayscale Bitcoin Investment Trust Eligible shares are publicly quoted on OTCQX. Investors can buy and sell unregistered but freely tradeable Bitcoin Investment Trust shares through their personal brokerage account in the same manner as they would other unregistered OTC securities.

Grayscale also recently launched a fund that invests in the digital currency Ethereum called the Ethereum Classic Investment Trust. 

Bitcoin ETFs will enter the market

Left also added he believes the SEC will soon approve other Bitcoin products such as exchange traded funds. We should expect cryptocurrency ETFs very soon. 

The Winklevoss Twins application to launch the Winklevoss Bitcoin ETF (COIN) ETF was rejected earlier this. The SEC citied a lack of regulation and surveillance-sharing agreements between exchanges. The twins have reapplied to the SEC for approval. It seems the bar is high for approval.

"Unfortunately, we are restricted from commenting under federal security laws," Grayscale told TheStreet.

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