I believe they are disabled, same with snow golems. I think it's to minimize the amount of lag produced on the server by extra entities that aren't really needed.

Can you create Snow golems? It would be really helpful for my town, I only need one.

Thanks folks! I was wondering, as I had done a search on the topic and found several old posts about using Golems for protecting your property. I guess it got out of hand with some folks fielding an army of golems...

These are the things I believe are disabled:

 golems, fire (admin only), breaking blocks via explosion (explosions can still cause damage to all mobs), TNT (except when fished out of water), creating obsidian from redstone dust

In addition there are some things that are still bugged.  I'm certain the staff is working on these issues if they have not already been deemed un-fixable.

I've made TNT, so it's not disabled, just that it's only good against mobs.