Writer's Dilemma: Is it Ok to write about your friends?

Only a few of my friends know about my secret life as a writer of erotic spanking stories. In a way, the secrecy makes the writing more fun.

It also gives me the freedom to use them as inspiration without worrying about them ever finding out...because if I do use them for inspiration it's usually to mock them.

Aren't I a great friend?

For example---one of my friends is an unbelievable snob and social climber. Although she's very successful, she still worries about impressing others. Basically, she's a starf*cker.

I'm not sure whether to be annoyed at her shallowness or to feel sad for her because she is so insecure.

I used some of her real life statements as the basis for two of my stories which were published on Discipline and Desire Judge Not: Class Reunion and Judge Not: Family Gathering.

I do have one "rule" though---I make my characters physically very different from my friends because it really freaks me out to write a sex scene where the characters resemble my friends.

Fortunately, even when a character is based on someone that I know, they still take on their own persona so that by the time I get to writing the erotic parts of the story, it's about the characters and my friends are long forgotten.

What about you? Do you ever include your friends in stories? If so, do you tell them? Do you have any "rules" that you follow about friends in your writing?