Starting in the mid eighties, I started to notice that a large percentage of my students confused the genitive with the plural ending: "Her parent's went to church. The grandmothers pies were the best." etc.
I could not figure out how exactly the collective American mind had short-circuited into this stuff, but the evidence was there before me every time I graded a paper.
Now, I'm doing it. So, all you current/former English teachers and editors: is it EVER correct to specify a plural ending with an 's???
I see this in technical writing ALL the time: "To broadcast a message, specify a list of url's for the destinations."
????
Joanna