[moses]

I don't know the whole deal with your request system but I see that it's at least somewhat automated. Isn't it possible to set it up so that, for example, any given artist can be played every 2 hours, but a given song only every 8 hours?

You might even want higher numbers there, but that's up to you. You're right though, the best solution is for everyone to experiment with new bands and see what they like. I know I've found a few new favorites with the "I never heard this band I think I'll request them" trick.