While Hannah and I are the unapologetic language nerds in the family, all four of us enjoy pointing out errors in spelling and punctuation to one another. Even the non-human members of House Full of Nerds get in on the copy-editing act (see Vintage Technology Obsessions, Preview of Coming Attractions). While this can be amusing, it also has its drawbacks - my laziness is only part of the reason I rely too heavily upon the computer versus the typewriter or pen. I don't place typos in the same category as spelling errors, except of course when I make them.
I also find that there's a slippery slope from smug superiority to "what is this world coming to?" horror. Hand-lettered signs with misused apostrophes get a snort and a "Well, clearly, they didn't have Mrs. Armstrong for third grade!" Use the wrong "your" or "their" and I might mutter that I could have sold you the editing services of my elder child when she was in seven. But occasionally I'll come across something of this magnitude: