Managing A Forum

[ZiNgA BuRgA]

I'm sure this varies with what you're managing.
For small forums where the admin wants to make it large, I'm sure the main challenge is getting activity.
You probably won't get many fights/trolls on small forums.  It's generally not so much of an issue on larger forums (though that depends I guess).  Spammers are usually more of an annoyance than anything else.

For this forum, where I couldn't care less about activity, I generally don't manage it.