Often a websites most useful resource is the people who use it. A discussion board allows these users to become members of the website and discuss things on-line. Users with a common interest can then share best practise in their industry, tricks of the trade and solve each other’s technical problems.
Discussion boards also serve a second purpose. Because potentially hundreds if not thousands of people contribute to the board it becomes a self-generating resource of information. This large amount of freely created content provides a large target for search engines to index. By doing this your website will receive many more visitors and be found under many more search terms. The added benefit to your members of having the ability to interact with other members in this way could prove to be a compelling reason to work with you.