Writer Problems #5: Do I ask...?

As a writer, almost anything can serve as inspiration for your creative works.
Sometimes you find yourself to taken with someone you want to translate them into a character in your works but are never sure how to tell them that you've done so.

Will they be flattered by their influence on your work? Will they despise the character and take it as a negative reflection on them?
I mean it's probably best to not tell them if you're used them as inspiration for a villain... Do you tell them or not?

Have YOU ever written a character based on someone in your own life?
Let me know in the comments section below...