Message boards are things that many people visit religiously for news. Often people become regular forum visitors even before they visit the rest of the site that hosts the forum. These people can be driven to a site's regular content and monetized in that fashion. Suggestive topics can be introduced via forum pages themselves and forums can serve as a cheap means of promoting other content areas on a site that is the real money making centers.

2. Message Boards are loyalty and brand builders and could be helpful should one later choose to market services or products in your industry if you are not already.

It is only natural that the sites people hang out regularly are going to be the sites people pay attention to more. If there are thousands of companies providing a given service but a person's favorite message board supports one more than another this is something that forum users take note of. Forums that people spend lots of time at have built up a certain level of trust. This trust carries over into related products and services the forum's owner may market themselves or endorse.

3. Message Boards allow one to keep an eye on people important in your industry via them gathering in your forum.

No matter what industry your site is involved in when topics are started about companies and people important in your industry often the people being discussed will show up to add to the discussion. This allows a forum to give an element of prestige to a site. When important people to your niche start to make your site forum a regular place they visit they become defacto supporters of your site as a whole. When new ideas or problems pop up people will discuss them often at the forum where influential people gather. If thats your forum this can only be a good thing.

4. Forums are good feedback centers, and can allow a webmaster to be able to better prioritize non forum content according to what forum members are talking about most.

If a forum begins to see lots of topics about a given problem or concern of your industry you can use this knowledge to create regular non forum pages about these topics with your content and your solutions and advertising. Forums can provide an easy ready made list of niche topics that people that visit your site are interested in. Without having to research and search for what is out there you can know via what your forum visitors posts just what kind of information they really want. Polls are relatively useless for gathering informatino about what a site's visitors really want to see in the future. Forums by their very nature require people to actively post the ideas and problems that interest them without being able to select from a predetermined list as polls do. This gives them their value as real and useful feedback for possible site additions.