If you haven't heared about Gamification see Wikipedia...a great example of Gamification is the badges on Huffington Post based on activity, sharing etc. The main purpose is to increase the activity of the users and their activity. Various big forums have used gamification actions (example: Gaia Online).
What do you think about this "system"? Can be useful on a community?
It CAN be useful to increase activity within your community...now, whether or not it's the kind of activity you want, I don't know. A lot of these systems simply reward trolls for posting nonsense. But if you have a decent community, it does give them something fun to work toward and can produce great results.
The award can be used not only for posting, but for inviting users, connetting with social, logging (example: badge on 2° login, badge when you connect minimum 1 hour 5 times etc.). I'm agreed with your opinion but users love that, see for example the social games on Facebook.
What most annoys me is gamification in games (e.g. achievement systems). That basically means the game isn't fun so achievements are put in place to give players another reason to play. Gamification is a problem when it becomes a substitute for more substantive motivators.
The GAME thing with forums has been flogged to death over the years. They had a time with some success, like forums running Gaming Servers, Teamspeak for live chatting and Clans to join. But people now want to be playing the games, not talking about them on some forum. Not unless they are boring to play, then who wants to talk about them on a forum if they are?
i think it can be a great thing to encourage participationits and rewarding your more active users
i use the usergroup promotion hack to achieve this on my own xf.
the rewards are not graphics or some sort of obvious distinction. instead various features are unlocked over time, such as signatures, custom user titles, moods, albums, etc.