There are lots of people who really don't like having their picture taken, or are actually afraid of the idea. And most of the time this probably stems from the worry that they just won't look good.
This is where the right sort of professional photographer can really help. First of all, an environmental portrait greatly increases the odds that the subject of the portrait will be relaxed, and that's most of the battle right there. A good professional also knows exactly how to set up a shot to show everyone at their best advantage.
So rest assured, if you're camera shy or want a portrait of someone who is, you can still end up with a great and unforgettable image.