The certificate is issued only after 2 blockchain confirmations (that is why we email it later because this takes about 15 to 30 mins). It is also available on line on stampd after that!
From our perspective a fee is essential both for the transaction miner fees but also to prevent blockchain bloating.
Regarding the certificate forging: Our certificate only refers to what the blockchain shows. We decided to issue such certificate in order to allow the user to easily refer to the stamping. It is the blockchain that cannot be forged!
Your suggestions are all very interesting and we are grateful for sharing. We will certainly explore them further. We are fascinated by the potentials of blockchain's public ledger and of course these and many more ideas could have outstanding applications.