Adding my take here.
Broadcast-domains should always contain ports that are similar and can always fail over to each other. They should NOT contain any unused ports or ports on different VLANs (as already indicated). Why? in a LIF failover scenario, if configured, can go to any port in the Broadcast Domain. I have had customer accidentally leave everything in the same Broadcast Domain and when the switch failed, the port moved to another on a differetn VLAN (so link was good, networking, not so much) and all communications stopped.
When you configure a LIF to have a "failover-group" (which is a leftover term from before Clustered ONTAP 8.3 ), and you have the LIF failover policy set to "broadcast-domain-wide" then all ports in the broadcast-domain *must* be in the same VLAN.
Depending on the platform, I might do something like have e0M and e0j in the same Broadcast-domain. e0M is active and e0j is hooked up and on the same VLAN (access-port on the switch) but just not in active use.
For the BD groups, when defining VLANs, I try to keep all the ports in the BD with the same tagged VLAN. In the example, there is reference to e0M and e0x-1111 in the same BD. Not ideal from the standpoint that Active-IQ and even Config Advisor will through a caution/warning since the LIF failover will switch from an access-port to a tagged vlan. The other examples appear to be fine (expect I would merge all four ports into an LACP channel and then tag the VLAN on the ifgrp)
With all that said, if you have a 100% flat network and do not use any VLAN tags, then you can probably get by with the Default.
If you have multiple subnets and/or you have VLANs, if you want failover to work without an issue, you MUST define a Broadcast-Domain for each Network (i.e. each subnet, like 192.168.1.0/24 and 192.168.2.0/24). Additionaly, if you are doing things like VMware over NFS or iSCSI, it is usually best to use an MTU of 9000 (as long as the network infrastructure supports it!) and you can define the MTU at the broadcast domain.