Groan. This was posted by one of my college friends on Pinterest today:
"If you know a loved one won't be able to make it to your wedding but you
 still want them to have an invitation (without the pressure of sending a
 gift), add a note along in the envelope explaining that you are sending
 it as a keepsake."
So... "I'm not actually inviting you to my wedding cause I don't think you can come, but I just want you to know I'm getting married and you can keep my invitation!"
Really? 
Pinterest makes me cringe.... a lot.