Muphry's Law: the inevitability of typos in discussions of proofreading

Muphry's Law, as formulated John Bangsund of the Victorian Society of Editors (Victorian as in "from the Australian state of Victoria" not as in "pertaining to 1837-1901, the period concurrent with the rule of Queen Victoria") pertains to the inevitable petard-hoisting that occurs whenever you mention proofreading or editing.
1. if you write anything criticising editing or proofreading, there will be a fault in what you have written;

2. if an author thanks you in a book for your editing or proofreading, there will be mistakes in the book;

3. the stronger the sentiment in (a) and (b), the greater the fault; and any book devoted to editing or style will be internally inconsistent.

Muphry’s Law (via Kottke)

(Image: Typo, a Creative Commons Attribution (2.0) image from mmitchell's photostream)