Watermarked ideas

Apparently dictionary publishers play Balderdash just to see who copies their work, making up random words and meanings. If another dictionary turns up with that unword in it, you know they copied from this particular dictionary. It's like watermarking ideas to see who copied you. Cartographers do it to their maps, too, introducing little mistakes that let them see who has duplicated their hard work for their own profit. It's a clever and subtle kind of watermarking, for sure, but it can have drawbacks. For instance, because this type of watermark needs to look like real data in order to work, it can foul up actual use of the data. In the case of dictionaries, sometimes people start actually using the fake word as if it were real, and that nullifies the purpose because now the word belongs in other dictionaries.

Mokalus of Borg

PS - I don't think there have been any cases of people changing reality to match faulty maps.
PPS - Mostly because that's the hard way.