I'll start with my favorite "love to hate" punctuation error, the "plural apostrophe". In England it is sometimes called the "greengrocer's apostrophe" from the habit of grocery store managers (or at least their sign-writers) who write signs like "Cucumber's $1.00" and "Banana's $1.50/lb".
The rule is so simple ("apostrophe-s" is used to show possessive) that I simply can't understand how so many people get the idea that all plurals ending in "s" need an apostrophe. Richard Lederer and John Shore in the apostrophe chapter of Comma Sense discuss the misuse of apostrophes in house signs and mailboxes. Mailboxes commonly have people's names like "The Smith's" and "William's". The second example is doubly in error because, since the mailbox presumably belongs to a family with surname Williams, the apostrophe, which shouldn't be there to start with, is in the wrong place. But at least Williams looks like a plural word. Some go beyond the plural apostrophe and feel that no word ending in "s" should be allowed to go apostrophe-less. To continue the mailbox example, we sometimes even get "Jone's". Aaaarrrrgggghhh!!!Now here's an interesting example of my own:
a) I am going to Smiths.
b) I am going to Smiths'.
c) I am going to Smith's.
This sentence leaves out some words that are implied or meant to be understood. Each of these sentences could be correct, depending on the words left out. Here are the full sentences with explanations:
a) I am going to visit the Smiths. (a family with surname Smith)
b) I am going to the Smiths' house. (the house belongs to a family named Smith)
c) I am going to Smith's house. (the house belongs to a guy named or nicknamed Smith)
To give the plural apostrophe writers a bit of a break, there are examples when an apostrophe-s is used to show plural. However, these situations are extremely rare and can't have spawned the ubiquitous plural apostrophes (can they?). Anyway, here they are:
- the plural of letters and numbers: "Mind your p's and q's" and "How many 3's are in your phone number?" Apostrophes, however, are not needed for the plural of dates or acronyms e.g. 1900s and DVDs.
- the plural of some short words like do. Dos, I suppose, could be confused with DOS (and I'm old enough to remember using it before Windows) so do's it is.
There is another excuse we could give for plural apostrophe writers. According to Lynne Truss, prior to the 19th century apostrophes were used, quite correctly, to show the plural of foreign words ending in a vowel. She gives the examples of words like folio's, pasta's and - yes - banana's. However I doubt that the average grocery store owner knows this fact. Hey, I own a health food store and I didn't know this before.
The confusion between the words its and it's is such a common problem that it's only right to give this error its own paragraph. Here the apostrophe is used only for the contraction of "it is". The possessive pronoun its does not need an apostrophe any more than the other possessive personal pronouns like his, hers, ours, yours and theirs. Simple, right? Now to confuse you again, the possessive of indefinite pronouns like anyone and everybody do require an apostrophe: "It's anyone's guess why everybody's use of the apostrophe is so mixed up".
I invite you to share in the comments some humorous examples of the misuse of apostrophes that you have observed.