[hjalle]

Funny experiment and perhaps also useful, but there are crawlers with good intentions[1] that still may ignore the disallows. I don't know of anyone else than the internet archive though.

[1] https://blog.archive.org/2017/04/17/robots-txt-meant-for-sea...

[zaarn]

Those crawlers can almost always be recognized by the UA.

[hjalle]

Yes, no doubt.