There seems to be no real rhyme or reason one board does better than others. And we have to accept the fact people migrate, they get bored, and look for something new. My forums are more content than posts. People visit and read the how to's and move on. High page views, low posting. If you want a chatty board, you will have to find the happy medium. Most boards have many more members than posters. You'll get lil groups that use your board to stay in touch with each other. I've seen boards that were VERY busy turn into ghost towns. Why? Who knows..People have short attention spans, they get bored easily. If you have a thriving site, your board will reflect it. Don't try to just have a board and nothing else. It will never really get off the ground, unless it has content that is desired. For example, the Ford-Deisel board (a UBB site) has lot's of archives filled with needed info for dealers, parts people and shade tree mechanics. They use it as a reference and a place to obtain answers, etc..
I read one post somewhere if one more Anime board opened the writer was going to scream. Find out what is being sought after and see if you can fill the void. Copying the ideas of other boards, and making "yet another of the same" you'll blend in and won't stand out. In short you have homework to do, it all depends on the amount of work you are willing to do. (you can have a succesful board or a life..LOL Not both..[just kidding])
