That kind of integration error is very easy to make, and the attention spent on it by in taking the extra care to avoid it probably really adds up, when aggregated over everyone who uses this kind of tool. e.g. I noticed today that ant does the same thing: it will output a literal "${filename}" if filename isn't defined.

In this specific case, Mailchimp could check for non-existent fields.

It would be even better to have a way for the fieldname to be automatically modified when you changed its name elsewhere... but because the naming is itself used to define the binding, there's no way to do this automatically (unless all the components were in a giant all-seeing IDE that automatically refactored all related components, wherever they be).

BTW: What I got from this story was that it's OK to screw up - I think productivity can soar if we don't spend endless attention checking things because we live in terror of making a mistake.

I don't think its OK to screw up, but in the event that you do screw up, step up and take accountability for it. This all boils down to being honest with your customers.

Of course, to screw up is to err (by definition), but I meant it's OK in the sense of it not being the end of the world. Your humour is an illustration of this. It's possible to get hung up on avoiding mistakes at all costs - indeed, at greater expense than the mistakes themselves.