Actually, a Googler informed me that the reason for the buildings' disappearance is due to lack of photo texturing. Please see this link for more details on this. (The real reason is aliens, we all know, but this makes a good alibi for the general public).
Are your building models disappearing? Do you need inspiration to go on? Look at this link and this one too. (Many currently accepted Google Earth buildings began as un-textured 'paint bucket' models, but went on to live long, happy, and successful lives as photo textured models).