What is an outtake? An outtake (also sometimes known as a blooper or behind the scenes shot) is an image or set of images which are not released in the original set of photos, and are typically "discarded" during the editing process. It's often, but not always, for the sake of humor.
A personal look at why I share my outtakes: I believe even the bad or unintentional shots are part of the process, and it usually reminds me not to take things too seriously and to enjoy what I'm doing.
What do I share? I usually share selected images that either I or others can learn from (i.e horrible mistakes), or shots that captured something funny or interesting (but not what the assignment was about). Occasionally, I will also include "behind the scenes" type shots with my outtakes.
My experience: I've found that people really enjoy viewing the outtakes. Sometimes it may be a behind the scenes shot to a shoot that gives people a little insight, while others might be something funny and lighthearted that reminds us of reality such as a pretty model making a not-so-pretty face. On portrait sessions, I've even had clients order prints of some of the outtakes. While a certain photo may not be one of "the shots", it doesn't mean it's not worth showing. I would, however, recommend to be choosy with the outtakes, as you wouldn't want to show too many of them and overload viewers with bad shots. Because in the end, you still want your best out there. Keep in mind that outtakes are also not for your portfolio website, but much better for a more personal and less conservative site such as a blog.
Link: View some funny outtake photos from i heart faces weekly photo challenge: Hilarious Outtakes