Minecraft Server?
I know a lot of people on these servers have Minecraft.
We ran one before. It was a ghost town.
The biggest problem with Minecraft is just the amount of management required.
Either you have a private server limited to just the people we'd trust not to grief, or we make it public and have to deal with everyone's complaints that player X or Y destroyed/stole their stuff.
To solve this, you get into the realm of server plugins, and then that becomes an entire management mess on it's own.
Did I mention the incredible memory usage of the server?
In short, I don't think it'd be worth it.