I agree you cannot make risk linear with dollars. What I tried to say is that they try to make inconvenience linear with dollars, so that one shouldn't generalize from the fact that one can take a few 1000 out of the bank in cash and put it in again a few months later without anything happening.
Well, even that's not right, but I do not have time to be more articulate right now.
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.