This is working well on my forum, and it can apply to forums of any niche. If you have an off-topic section, make threads such as word association or where is this place (where subsequent posters must identify the location of a posted picture). The latter is especially engaging. A good list of forum games: http://www.gamelair.com/gameforums/forum-games/
Yes, this can lead to frequent activity. But it can also lead to a flood of worthless posts. Good for boosting post count and frequent posts, but the content you create as a result is of no value. I suppose if you can be a little more inventive and create "games" relevant to the niche of your forum, it might help a little more beyond just inflating post counts.
Agreed. And if it's a niche forum the people who find it are usually interested in the primary topics of discussion anyway.
I have to agree with you that the quality of posts won't be that high. Though I suppose you could attract new people to the forum like this.
My forum has a games forum which contains around 18,000 posts (total posts: ~400,000) I don't find it helps that much to be honest, but that my just be my audience. It does get used, but no where near as often as the other forums.