Have you ever ran into to problem that your alerts are not sent anymore? When you were looking for them, they seemed to be deactivated? Yes? You're not the only one. This is the solution:
To reduce the load of the server, SPS and WSS have limitations for sending alerts. Standard, in SPS, users can have only 15 active alerts. For every new alert after that, another alert willl be automatically de-activated. To change this in SPS, go to 'Site Settings' and then 'Manage Alert Settings'. Here you can change the number of alerts per user. In WSS, go the the virtual server settings.
Ok, I'm happy I found this, are you?