You can also see it on (the absence of realistic) city views.
It's also almost impossible to upload buildings on BigStock, SS or IS unless not as main focus. Must have to do with the warranty. DT is still very lenient on it. The warranty was really a bad move (DT hasn't one) as buyers are responsible for the use and many times they don't need that warranty.
Maybe they are being over-cautious?
Regarding copyright: from what I understand of British and German laws, architects' drawings are copyright, not buildings. So you cannot copy a design but you can shoot a building.
Regarding property: from what I understand of German laws, a property release is not required if a building is shoot from a public and publicly accessible point of view.
Regarding safety/anti-terrorism issues: the UK tried to impose limits on photography in public, but it's regarded as an unlawful request by many MPs and lawyers as well.
Other countries may have different rules.
So many pictures of buildings *could* be legally accepted without a release.
But I'm not a lawyer, it would be nice to know for sure so that we can sell pictures of buildings at least on our personal websites if agencies don't have the pulse to read local laws and act accordingly.
Any lawyers here?