I received a reply back from petr at IE. He not only sent me an email but also posted in on the IEOC forum.
I am going to post it verbatim from petr. See below. Also going to add this to my ongoing list of CCIE notes.
Basically, you need the broadcast keyword in the following cases:
1) You need to run a control or management plane protocol across NBMA network and is uses multicast/broadcasts. Usually this the case with EIGRP, RIP, OSPF broadcast/p2mp networks. If you are explicitly told not to use broadcasts with FR mappings, use static neighbors for RIP/EIGRP and non-broadcast network type for OSPF.
2) You need to delilver multicast across the NBMA cloud (you need the broadcast for either pseudobroadcast solution or PIM neighbor to come up)
3) You are asked to tune some feature related to brodcasting, e.g. Frame-Relay brodcast queue.
As you can see, brodcast keyword is basically needed either for control plane traffic or some specific feature. If you are not explicitly told anything about broadcast mappings, review if any of the above applies to your scenario and configure appropriately.
