@Empire: It also depends on the type of content. If a forum has a games / chat section, people will post a lot more. In this case, it is perfectly normal to generate 300 to 500 publications per day if you have 2 dozen active members. The disadvantage is that your other sections could suffer. However, if this keeps your members entertained and interested, especially a small site, this is not a bad thing.
It also depends on your user base. Our forum does not allow it because of our past experience in the field of entertainment and games lol. That's why we have a lot fewer messages daily, but we are still active. We have a private section of fun and games for donors / founders, but no one writes much about it. XD.
We have exactly 300 atm members – I would say we could have 60 to 70 people actually connecting each week, and then there are others who are occasional posters. Our community (not the forum) is very old, so we have a few who do not send much, but like to stay in touch with the community from time to time.