Following a good will Casascius apparently opened the pandora box. Now people are really believe that the sealing proves that the physical bitcoin is secure. But of course it is not. A producer of a physical note or a coin can copy and preserve the private key. This situation is so strange. I bet that if this hysteria wouldn't decline we will face a wave of fraud associated with a physical pseudosecured coins in a future.
It would be better if Casascius spend the same amount of effort populating the idea that only self printed paper wallets are secure. Every such cold storage obtained from a second party as a present, gift or a payment should be immediately transferred to the safer wallet because private key could be copied and preserved by a grantor. Tamper-evident seal in this case doesn't provide the needed level of security because the private key could be copied before the sealing was applied on a coin.
Shame on you Casascius

It is an open market. You do not need to purchase Casascius or any other physical Bitcoin. Purchasers put their trust in a supplier which could maintain that trust or violate it. Now Casascius coins are now more valued for the collectable value than the Bitcoin preloaded on them. If you think a supplier will steal the Bitcoin, do not purchase from them.
I personally trust Casascius.