I am using Panoramio JSON Photo API since quite some time.
Well, during last weekend they have a major maintenance of their platform.
Unfortunately after this maintenance the API format has been changed without any notice, It took me half a night to realize what was happening and fix my mash-up application.
I have filled a report here ( http://www.panoramio.com/forum/viewtopic.php?p=239662#239662 )
Lessons learned : If you are using any third party APIs - have a plan and be ready for surprises !.