Vanilla has a couple of problems which translate to a huge amount of effort on the part of server owners and moderators - grief and crowding. Until now, griefers have forced moderators to investigate reported griefing incidents, roll back changes, and ban offenders, only to move on to the next incident because there's a never-ending supply of griefers. Also until recently, any successful server has a crowding problem, both in the world because players fill up the space around the spawn making it impossible for new players to get started, and also we just run out of player slots and players can't reliably log in.

Today, it's possible to run a public server that's seriously low maintenance. You need two Bukkit plugins:

1. GriefPrevention. It blocks all kinds of grief, and it's self-service so players are responsible for protecting their builds. It's easier to use than similar alternatives (WorldGuard, Residence, Precious Stones, Lockette, and so on), and also more effective. In addition to build/break grief and theft, it also blocks spam, tree topping, forest fires, spawn camping, and server advertising. You can use land claim blocks to monetize your server. It can also integrate with economy plugins.

2. PopulationDensity. It automatically moves your spawn when it detects the area around the current spawn is getting crowded. It never moves the spawn to an area where there are no resources, like an ocean, field (no trees), or desert. It's fully-automated. It also boots idle players to make space for active players, and queues players when the server is full to ensure login fairness. You can use login queue priority to monetize your server.

I've been running only these two plugins on my server for two months now, and despite daily bumps on planetminecraft (which invites a flood of jerks, griefers, and morons, in addition to desirable players), I am the ONLY admin, and I still have time to kick back and actually play Minecraft on my server. I've built several builds, and only rarely answer some questions or ban a player for misbehaving in chat (trolling).

If you don't have these plugins, you're making your life unnecessarily difficult. At least look into them, I think you'll be very glad you did. Other plugins you may be running could add to your administrative overhead, but I think these two solve the biggest, most common problems on public servers in a way that doesn't translate to work on the owner's behalf.

They're both on dev.bukkit.org.