Cameron and Tyler Winklevoss are forming an exchange-traded fund (ETF) for bitcoin, the alternative currency in which they hold a large stake.

The twins, best known for their tangential role in Facebook’s founding, just filed the paperwork for a public listing of the Winklevoss Bitcoin Trust at a proposed valuation of $20 million. That’s equivalent to about 236,000 bitcoin at the present market value—which, incidentally, fell about 10% today in a typically volatile day of trading. Pricing the IPO, if it ever comes to market, will be tricky.

But that’s hardly the only odd aspect of offering a bitcoin-based ETF. Though all securities carry risks, which must be disclosed to investors, the ones listed in the Winklevoss prospectus are unique:

The trust may not have adequate sources of recovery if its bitcoins are lost, stolen or destroyed.

and…

The loss or destruction of a private key required to access a bitcoin may be irreversible. The trust’s loss of access to its private keys or its experience of a data loss relating to the trust’s bitcoins could adversely affect an investment in the shares.

Though the digital currency itself has never been hacked, the same can’t be said for the wallets in which people store bitcoins. The biggest concern for anyone who wants to make a livelihood out of bitcoin is always security. How do you keep digital wallets safe?

The Winklevoss Bitcoin Trust says it will use a proprietary security system, stored within the vault of a US bank, to hold the private key that would grant access to its bitcoin stash. But besides questions about how secure that system really is, investors also have to think about what it means to be storing bitcoins in a US-based bank. The trust states pretty clearly that it will bend to the whims of US authorities, so are bitcoins likely to be safer investments outside of the country?

It may be illegal now, or in the future, to acquire, own, hold, sell or use bitcoins in one or more countries, and ownership of, holding or trading in shares may also be considered illegal and subject to sanction.

While it hasn’t been outlawed, bitcoin still operates in a legal gray area. Many people who actually use the currency to do business are engaged in illegal activities, and determined criminals can find ways to use bitcoins to launder money without being discovered.

So far the US government, which spearheads a lot of the world’s anti-money laundering efforts, hasn’t thrown the book directly at bitcoin. But it’s gotten close. In May, US authorities turned to Costa Rican police to help shut down Liberty Reserve, a virtual currency and exchange that allegedly encouraged criminal activity. Earlier that month, the government froze assets in accounts held by the most popular bitcoin exchange, Mt. Gox.

There’s more:

If a malicious actor or botnet obtains control in excess of 50% of the processing power active on the bitcoin network, such actor or botnet could manipulate the source code of the bitcoin network or the blockchain in a manner that adversely affects an investment in the shares or the ability of the trust to operate.

We’ve heard plenty about activist shareholders, but a bitcoin activist would take the concept to a whole new level. Essentially, some investor or coalition of computers could potentially amass enough processing power that it could decipher the encryption system bitcoin uses to operate. That would allow it to spend funds multiple times and prevent further transactions. At worst, this would render the whole currency pretty much useless overnight.

Not the risks typical trustees have to think about.

Correction: A previous version of this article implied that a malicious actor or botnet could manipulate the source code of the bitcoin system by amassing a large number of bitcoins. That has been change to reflect that it would actually need to amass processing power, which would bring it power over bitcoin’s encryption system, not its source code.