I think Dan Bernstein is an absolutist, in the sense that he believes error-free ("invulnerable") programs are commercially achievable. I don't agree, but I think his perspective sheds some pretty valuable light.
I'm somewhere between the two of you: I think error-free programs are achievable, but I realize it's a huge amount of work and it's impossible to ever know for certain if you've succeeded. I see capsicum as something to help bridge the gap between "I don't think there are any bugs in here" and "this program is safe to run".
