Speaking on CNBC on Dec. 11, 2017, securities regulator Joseph Borg said, "We've seen mortgages being taken out to buy bitcoin," adding, "People do credit cards, equity lines."

The cryptocurrency, which began the year trading at around $1,000, has surged to around $17,000 at the time of writing.

Borg is president of the North American Securities Administrators Association, a voluntary investor-protection organization, and director of the Alabama Securities Commission. 

"This is sort of the mania phase of it," Borg said Monday, comparing the current enthusiasm for bitcoin to the Dutch tulip mania and the failed bitcoin exchange MtGox. 

Bitcoin's parabolic rise in recent months has attracted unprecedented amounts of attention from the media, ordinary investors, Wall Street and regulators. Bitcoin futures started trading on the Cboe exchange on Dec. 10, 2017, a milestone that has been widely taken as a sign of bitcoin's growing acceptance. (See also, Four Problems with Bitcoin Futures.)

People who are just now hearing about bitcoin should read up, though. For those who think this is a bubble of the sorts last seen in 17th-century Holland, check out bitcoin's 50,000-percent rise in 2011 and again in 2013. Having surged just 6,000-something percent since its last big drop, bitcoin may just be getting started.

To the moon, you say? Buy, mortgage the house, buy some more, set up a mining rig, buybuybuy? Before you do, keep in mind that when bitcoin crashes, it crashes like few other asset classes can. Following the MtGox debacle, it fell by 82%. In 2011 it fell by 92%.

For the iron-stomached hodler ("holder," to the laity), that kind of drop is unnerving, but familiar. To the poor sap who just mortgaged their house to get in on the action, it's something else entirely. (See also, Bitcoin Bulls, Bears, and More Bulls Square Off in New York.)

Leverage is cropping up all over the place in bitcoinland: bitFlyer (MtGox's successor as Japan's largest exchange) lets investors buy up to 15 times their cash deposit, according to the Financial Times. That's a bit ironic, because the blockchain itself won't let you borrow a cent: you can spend the bitcoin you have at your address and no more.

In the face of such eye-popping returns and eye-gouging reversals, the best thing to do is learn what you're investing in – or staying away from. If you haven't heard of MtGox or its walking, LARPing PR-don't of a founder, you may be straying outside your circle of competence. Same goes for hashes and nonces and blockchains and proof of work and forks

Here's one place to start. Here's another. Don't mortgage your house to buy bitcoin.

Disclaimer: the author owns bitcoin.