The approach that I adopt depends on a lot of factors.
1. Is the activity on the forum high or a bit slow? This is the major part that will make me decide on how to approach my activities on a forum that I own as I wouldn't want some members mess things up for me.
2. Do my forum experience spamming and attacks? There are occasional attacks on forums and watching it from afar instead of being active can be a wrong decision to make. So, I get involved always.
If you have staff members who are very active on your forum, they are going to be more than capable of taking care of any cases of spamming and trolling in your forum.
It's external attack you need to be worried about because those kind of attacks are capable of taking down your forum if you don't fight it head immediately.