People usually put them in when they don't belong...
Hope all the mother's out there have a great day
The dog was chasing it's tail
Apple's for sale
Leave them out when they should be there...
Tomorrow is my dads birthday
Its going to be a great year
Or put them in the wrong place...
My friends' dad is really cool
It's time for my husbands' birthday
I've found that people are way more likely to put apostrophes in when they don't belong rather than put them in the wrong place or leave them out. The worst offense is the its/it's/its' issue.
I am really not an apostrophe snob...well, maybe a little. I don't want people to be paranoid about their writing around me!
At any rate, apostrophes are important. I was delighted when a coworker (and Facebook friend who has NOT unfriended me!) posted this on her wall--the Apostrophe Song!
Enjoy--and if in doubt about an apostrophe, look it up (or feel free to e-mail me to ask!).