I haven't seen any empty houses or cabins or ruins. I had a lot of fun in those structures, even in other games like oblivion and such, but FFXIV's zones are focuses on 'wilderness', so you won't be seeing many structures. Unless they release a new zone with structures in it :)
If you're talking about empty houses in cities, there are many functionable buildings (mostly guild buildings). I have not seen embassies or residential NPC-houses yet. They may be locked off, but the locked off city areas are airship docks and high-tier places (akin to the tree from windurst and the mines from bastok, and the castle from sandy).
There may actually not be houses or structures scattered about in this game. Is it a big deal? You decide. I can see where you're coming from though
(There will be player housing like moghouses, but this is not what the OP is talking about)
Edit: there are not broken-down structures like the building in saurumuge, or the foundations in sandoria's starter zones, or camps and huts, or whatnot. Like I said, these zones are more based on wilderness.
I think it's pretty cool but I do like my zones in any game to have an interesting amount of structural variety.
Edited, Sep 13th 2010 1:52pm by DirectorCobbs
Requested self-ban from admin. Later guys, good luck