The Bitcoin Mines of Iceland There, more than 100 whirring silver computers, each in a locked cabinet and each cooled by blasts of Arctic air, are the laborers of the virtual mines where Bitcoins are unearthed. The custom-built machines, running an open-source Bitcoin program, perform complex algorithms 24 hours a day, seeking to win a block of 25 new Bitcoins from the virtual currency's decentralized network. Emmanuel Abiodun, 31, founder of the company that built the Iceland installation, called the computers "money-printing machines." He is one of a number of entrepreneurs who have rushed, gold-fever style, into large-scale Bitcoin mining operations in just the last few months, as a speculative mania has helped push the price of Bitcoins higher. These entrepreneurs are making enormous bets that Bitcoin will not collapse, as it has threatened to do several times. If the system did crash, the fancy computers would be essentially useless because they are custom-built for Bitcoin mining. Mr. Popper writes: "The computers that do the work eat up so much energy that electricity costs can be the deciding factor in profitability. The virtual currency's true believers "are taking the long view - the one in which Bitcoin, despite the ups and down, keeps appreciating in value and eventually becomes a serious currency," Nick Bilton writes in the Disruptions column on the Bits blog. Paul Krugman, in his column in The New York Times, writes that the appeal of Bitcoin is similar to that of gold. "Bitcoin seems to derive its appeal from more or less the same sources, plus the added sense that it's high-tech and algorithmic, so it must be the wave of the future," Mr. Krugman writes. The Fed said in its guidance that it would "strongly scrutinize" risk-transfer deals that have a substantial impact on a bank's balance sheet. Banks that have recently used such transactions include Citigroup, Credit Suisse and UBS. Supporters of these complex deals say that they allow banks to protect themselves from future losses on loans or other assets. But regulators are concerned that banks may at times use them to evade the stiffer regulations that have been introduced since the 2008 financial crisis," Mr. Eavis writes. While risk-transfer deals have been around for years, the temptation to use them has risen as regulators have required banks to increase their capital. Mr. Icahn's deal helps show why. The investor paid at least $2 billion last year for 82 percent of CVR, an oil refinery business, something he knew little about. He then tried to sell the company quickly and failed. Yet this year Mr. Icahn took advantage of an M.L.P. structure and used the company to inflate his already enormous wealth. Mr. Gelles writes: "In January, CVR, under Mr. Icahn's direction, placed its refineries into a new company, CVR Refining. Thanks to those generous distributions, stock market investors are valuing M.L.P."s at a significant premium to traditional corporations, so there was a good chance CVR Refining would do well as a public company." Data on personal income and outlays in November is out at 8:30 a.m. Please note that the newsletter will go dark for the holidays, to resume on Jan. 2. The DealBook site, however, will be updated regularly with news and analysis during this time. See you in the new year! The nation's biggest bank, JPMorgan Chase, had won the right to expand its reach in a lucrative business that has nothing to do with banking: electricity," Gretchen Morgenson reports in The New York Times. But with its June 2010 letter, the Fed let JPMorgan take an even bigger role selling electricity in California and the Midwest, saying the push would "reasonably be expected to produce benefits to the public that outweigh any potential adverse effects."" Sign up for the DealBook Newsletter, delivered every morning and afternoon. Mergers & Acquisitions  In agreeing to to buy Gentium, a drug maker, for about $1 billion, Jazz Pharmaceuticals took full advantage of that benefit. DealBook  The software maker allows brands to coordinate advertising across the web. Sunday Times Financial Times It can do so because real-estate loans were excluded from trading restrictions. But one major studio, Sony Pictures Entertainment, which has been under pressure from the hedge fund manager Daniel S. Loeb, did cut its slate for next year.