Weirdly, though I think that bitcoins will succeed (and accordingly have some) I don't think Calacanis' article is well-founded.
It struck me also as a rather shallow and hand-wavy article, and I was wondering what people who liked Bitcoin would think of it. (I am quite used to the feeling of wishing a particular advocate for a view of mine wasn't on my side.) I am not a fan of Calacanis; I respect his skills, I don't like his work or the quality of his ideas.
Tangential, but a subject of some local interest:
Why Bitcoin will fail by Avery Pennarun. "The sky isn't red." Thesis:
I'm not sure I buy these and am not competent to evaluate his claims on 3., but would like others' critique.
L019: Bitcoin P2P Currency: The Most Dangerous Project We've Ever Seen by Jason Calacanis. A rather more enthusiastic viewpoint of the project:
The actual text contains many more caveats than the eye-catching selection of points above.