I don't know... but I've had coworkers who are not professional programmers, but who wind up "helping out" with programming on the job, and I desperately wished that instead, they didn't know a thing.

Instead of them respecting my job more, they come to respect it less because they think they can do it just as well as I can. They think they're perfectly capable of forming time estimates because they insist "they" could do x task quickly, despite the fact that they're clueless about architecture, refactoring, documentation, testing, etc. They have no conception of why spaghetti code is bad, or what it even is.

Of course, this is all probably due more to management problems than anything else, but it is a very good example of "a little knowledge is a dangerous thing."

And as for the French analogy: I've known people who claim to speak French and then get themselves into hairy situations due to misunderstandings because they greatly over-estimate their skills and are overconfident in what they "think" they understood. It's equally infuriating.