I recently asked about getting inside of someone else's head for writing good characters who are noticeably different from myself and received some great answers. One answer suggested that you should absolutely not borrow traits from friends. On the other hand, over on a question about how to develop characters, an answer suggested to shamelessly steal personality traits from others.
My earliest attempts at varied characters used the shamelessly stealing personality traits approach. Unfortunately when I let friends read my work, it backfired badly. The reader would identify a character with one of his or her traits and assume I thought he or she had all that character's traits and that character was basically them. That meant that my friends thought I had a badly skewed perception of each of them and I ended up playing damage control.
So what's the solution and why? Was I just bad at masking my stolen personality traits or did I use too many items from a single real person in each character (an easy way to make a consistent character)? Should you never think of friends during character development? Should you think of them only to avoid them? I had a writing professor who told us about a perfect detail from a friend that she didn't use for a character because she thought the friend would be too hurt.
This is something that I think might plague myself and other writers without trait stealing. My mom thought my favorite character of all time was modeled on her when I hadn't thought of her at all during my writing!