Ahh okay, good insight. I hadn't even considered the Miiverse friend integration. I haven't tried that yet but it looks like that's how you add MH friends and sync up with them.
I'm not saying I have a problem with that as that's how XBox live works. However, there's a GAP in the feature. The gap is this - how do you actually FIND people you want to hunt with? What if you're not already friends with them? What if you want to be friends with someone say, in just MH and not across all Nintendo games?
My cousin and I shared guild cards last night and although they're kinda nice and interesting, they're useless for friend-networking, because even after sharing a card you still can't send messages/warp to another player. They just give you very detailed info about a hunter.
Also on an aside I have to say that the chat box and lobby features are idiotic. The chat box because only 3 lines of text fit in it (where 6 should fit fine if the player's name were displayed to the left of the message like in Tri); and the lobby for a similar reason and because you can't do lobby searches.
I really hope Capcom can address these features and introduce updates for them in the future. We should get a list of things that were present in Tri but are missing in 3U and get that over to Capcom.