We use number of logs messages per minute to track how busy the sites we host are and we're seeing some strange behaviour from the Forum module. When a forum post is created hundreds or thousands of log entries are being created, it seems all users in the same course are notified of the new post and for each user that is notified a log entry is created. Then for each user who receives the notification another log entry is created to note that they received it.

Not only does this throw off our usage calculations, but it also seems to be creating performance problems on the sites of our larger clients. When the cron runs, thousands of these spurious writes are being made to the database at the same time as legitimate logging of real events is going on.