The editors of the Daily Mail didn't.
The analogy isn't perfect because the Federal Reserve "creates" more money than is actually printed, so the dollar is really a "virtual" currency as well. But the point stands that the total amount of _commitments_ made in dollars exceeds the amount of dollars that "exist" by any central measure.
The physical (virtual?) Bitcoin example would be: if you have an account with a Bitcoin bank and you make a transfer to someone else who's using the same Bitcoin bank, they don't have to generate a Bitcoin transaction to honor that transaction.
The virtue of Bitcoin is that it allows anyone to perform transactions in a way that only banks can do with dollars, but this is not the only way to perform transactions with Bitcoins any more than it is with dollars.
There are more $100 bills than all other types of bills put together. The majority aren't even in the United States.
As we all know, you don't have to possess a physical dollar bill to spend a dollar. There's no reason the same shouldn't be true of Bitcoins; you shouldn't need to "possess" a "real" Bitcoin in order to spend one.
On the other hand, people who are getting the monthly subscription would really be up a creek. If SonicBlue turns off the servers, all the monthly-subscription units will be permanently out of service within a week. They lock up and throw away the key. Hopefully some enterprising hacker would be able to cook up a workaround, but even then, the majority of consumers would be stuck with a $250 doorstop.
Another possibility, always present, is that an anti-DVR consortium could buy the product line and send out a "software upgrade" that disabled all the units, even the liftetime ones. I believe the service contract doesn't even prohibit this. It certainly says that any feature can be removed without prior notice. So why not all of them?