Should you keep several different portfolios tailored to specific purposes

One of the most common business mistakes is trying to show the world that you are a competent photographer. That will not help you; it is a given that anyone worthy of being hired to shoot professionally is competent.
What you must excel at communicating with every tweet, image, Facebook post, newsletter, meeting, exhibition, and tear sheet is what makes you unique and different from every other perfectly competent photographer with a 20+ megapixel camera and some expensive lenses.
You must choose a specialization. Believe me, it will be hard enough to compete in just one area. The industry is glutted with photographers. The first step is to identify the kind of photographs that you would love to get paid to take, the kind that hold magic for you, the kind that will continue to challenge you, the kind that arent going to lead to boredom and creative stagnation.