2. Customer Interaction
By monitoring brand-related activity on Quora, you'll soon get a sense of the most active participants within that topic area. Though it would have to be done very carefully and within the site's guidelines for acceptable use, you could potentially initiate further interaction with such users--on Quora or elsewhere--to address problems, recognize loyalty, or establish some sort of deeper relationship. I'm betting that Quora will likely develop brand tools toward that end in the long run.
With a ready base of participants who follow or at least are interested in your company or products, Quora also seems to offer promise as a platform for soliciting feedback for use in product design, marketing or other strategies. It will be important to watch as the site evolves, however, for a better sense of what is and isn't considered acceptable over time.
4. Customer Support