[zrail]

That's a fair point. So far there hasn't been any transcribing necessary because I have the customers reply to their receipt emails if they have a problem, but that's definitely something to consider if you have to do phone support.

[mikeash]

It's also useful for anything where they might retype the string. (Even if you tell them to copy/paste, some people will still retype.) Not that this necessarily applies to you, but for others considering similar schemes, avoiding I/1/l and such can be really handy.