Do apostrophes matter?

Meet the 'Grammar Vigilante' of Bristol

For years, it has been rumoured that somebody has been going out late at night, correcting bad punctuation on Bristol shop fronts.
The self-proclaimed "grammar vigilante" goes out undercover in the dead of night correcting street signs and shop fronts where the apostrophes are in the wrong place.
Jon Kay meets grammar's answer to Banksy and reveals the extent of his one man mission to improve standards.

 Look at what this 'vigilante' does: 

What do you think about it?