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But what are the consequences for not spending a small amount? Why are they concerned that the coins may not be redeemable?
I suspect that the main concern is the possibility of a printer error, or problem with your webcam. By spending a small amount you prove (mostly to yourself) that the printed scan code will be usable to spend the bitcoins in the future.
So when you say (mostly to yourself) you're talking about sending some from my address to another I also own (I assume).
No. I'm not saying send the coins "mostly to yourself". You can send them to another address that you own if you like. I'm saying that the purpose of telling you to send a small amount from the paper wallet is mostly to "prove to yourself" that it works so that you can have confidence that you will have access to the bitcoins in the future. If you create the paper wallet with 0.02 BTC and then send 1 BTC per month to the wallet for ten years only to try the wallet for the first time ten years later and discover that you are unable to access the bitcoins at that address, you will be quite unhappy. Better to find out that there was an error creating the paper wallet when there was only 0.02 BT in it than ten years later when there is 120.02 BTC in it.
That would be easy enough. I did read that doing this is a bad idea as I've had to use the keys online. But I suppose this is a worst case scenario where someone might intercept them in transit, which I would guess is very unlikely attack unless you have millions invested in btcs.
Agreed, spending anything at all from the paper wallet does reduce the security of the paper wallet a bit. Prior to spending bitcoins that are sent to the paper wallet, the public key of the address is entirely unknown and if you generate the paper wallet while the computer is offline, then the private key has never been exposed to an online computer either. Using the blockchain.info service for spending from a paper wallet does reduce this security a bit.
If you are comfortable and confident that the private key on the paper is the correct private key for the address on the paper and that it will therefore be usable in the future, then there is no need to spend anything from the paper wallet when creating it.
In the case of printer error won't scanning the QR codes not prove that they are valid?
That would tell you if the code can be scanned and decoded to a string of characters. You still wouldn't know for certain if the string of characters is the correct sctring of characters for the address that is written on the paper. There are technically ways to validate the private key without using it online and without spending the bitcoins associated with the paper wallet, but there is no user friendly method at the moment. Doing so would require some technical knowledge.
