Federal Reserve Chairman Alan Greenspan testifies before the Senate Judiciary Committee on the effects of the recent wave of mergers in corporate America, June 16. Greenspan told the committee that the economic effects of the mergers were difficult to estimate but noted that they were unlikely to reduce competition substantially. REUTERS Earlier today, former Fed Chairman Alan Greenspan discussed Bitcoin with Bloomberg's Trish Regan.

Regan got right to the point: "Is Bitcoin a bubble?" Regan asked.

"I guess so," Greenspan said, adding, "You really have to stretch your imagination to infer what the intrinsic value of Bitcoin is. I haven't been able to do it. But if you ask me, 'Is this a bubble in Bitcoin?' 'Yeah, it's a bubble."

People are baffled by this remark.

That's because Greenspan refused to call the housing bubble a bubble, and presided over the dot-com bubble despite seemingly having recognized it as such as far back as 1996, when he made his "irrational exuberance" speech.

Here's a smattering of the reaction from Twitter:

GREENSPAN CALLS BITCOIN A BUBBLE ASSURING ITS RISE TO $10,000 — Timothy Connolly CFA (@SconsetCapital) December 4, 2013

I would MUCH RATHER hear Greenspan call Bitcoin a bubble than not. He's never recognized a REAL BUBBLE of his own making (Y2K, housing, etc) — Cody Willard (@codywillard) December 4, 2013

Funny, I think RT @zerohedge: GREENSPAN SAYS OF BITCOIN: `IT’S A BUBBLE’. sigh — Brian Posner (@FrontOfTheHerd) December 4, 2013

Oy vey! Greenspan talks bitcoins, bubbles and bloomberg! (fine alliteration) http://t.co/pTXBr67B15 VT6fx8yBTOOQIAFlrraqDQ.html — Douglas Kass (@DougKass) December 4, 2013

Maybe Greenspan got religion since stepping down from the Fed in 2006. But of all the things to now call a bubble, when the evidence is mounting that it's not necessarily so: Bitcoin?