I think it was Susan at I Think; Therefore I Am who sent me these first signs. If so, thank you, Susan. If not, thank you, somebody else:
I found these on BuzzFeed:
This friendly request.
This lack of punctuation.
This reassuring sign.
This extremely descriptive sign.
This reliable champion.
This restriction.
This phone number.
This unnecessary labeling.
These generous souls.
And finally, this family planning advice.