Thanks for your reply Bill.
Again you are quite right about the fact that, after a given FQDN, it may be a lot of IP addresses. But this problem also applies to any FQDNs used all around the platform. There is no guarantee that two consecutive requests result in the same IP addresses returned and if you use them to have any sort of inter-dependence between them you could get undeseired results.
But I think it may be better to have this than nothing. Because of DNS caching it is very probable that two requests get the same result because they both may be using the same DNS server or even the pfSense itself as a DNS caching server.
Instead of the message telling that FQDNs are not supported a message could advert the admin that she should use the same DNS server for the pfSense and the internal clients and that using FQDNs is not fool proof because of the chance that two consecutive requests receive different replies.
I am aware of the problem of blocking access to youtube or other undesired sites by IP lists; that does not work and a different approach (protocol analisys) has to be taken instead.
But, unlesss the effort to put this into place is so high that makes the task unrewarding, being able to use FQDNs may have more advantages that inconveniences under my point of view.
Miguel.