Just curious, but has it ever been determined if these guys kept the secret keys after manufacturing the bills? These guys just seemed to disappear one day.
I originally had two full sets. I opened one and redeemed them on mt Gox without a problem. The other set checks out fine when querying the addresses.
He (Doug) did disappear suddenly. I think he lost a fair chunk of change. Not sure why he never came back. Perhaps he feared some legal issues? I never heard anyone have trouble with a BitBill...but I'm not sure how's my were ever made. It was kinda short lived. Still seems like a good idea, but I think Casascius coins work pretty well too.
Anyhow, I'm glad to have this bit of Bitcoin history.
