I'm vexed by agreement issues lately.
For example, an article I recently copy edited said something like, "The suites feature Jacuzzi tubs and a balcony." Here's another example, "Homeowners throughout the country should buy an insurance policy tailored to their unique needs." All parents should come to the school by 6 to pick up their child."
Besides aiming for clairity, the copy editor's job is also to aim for precision. So we have to think about possibly implying that multiple suites share a single balcony. We have to think about whether all homeowners can collectively buy a single insurance policy. We have to worry whether a sentence suggests that dozens or perhaps hundreds of parents all come to pick up one child.
The alternatives get messy, and writing around the problems isn't always ideal, either.
"Suites have Jacuzzi tubs and balconies" -- Making the items all plural is imprecise and can lead to potential misreadings. Does each suite just one one tub and one balcony? Or might some have more? From the way this is written, there's no way to be sure.
"Each suite features a Jacuzzi tub and a balcony" -- Making the items singular is often a handy way around the problem, but it can get very old very fast. And in some contexts it just doensn't work, like when you're talking about many different types of suites and keeping them straight means keeping them as groups.
That's what I usually try to do, though the result is usually far short of ideal.
Of course, I wouldn't change "All dogs have four legs" to "Every dog has four legs." But that just further shows the insidiousness of subject-object agreement.
It's frustrating because, in a job that offers some very solid satisfactions, there's no way to feel good about a lot of these situations. (Or maybe I'm just whiny because tomorrow the company I'm working for filed Chapter 11 but keeps swearing that I'll get they money they owe me. Yeah, that could be makin' me whiny.)