The same thing keeps happening to me. How do I stop it?
Actually it is not only apdb files but also the following:
...Dropbox/iPhoto%20Library/Database/DataModelVersion.plist
...Dropbox/iPhoto%20Library/Database/tmSync.plist
...Dropbox/iPhoto%20Library/Database/SpanCache.plist
...Dropbox/iPhoto%20Library/Database/ZoomLevelCache.plist
...Dropbox/iPhoto%20Library/Database/VersionGroups/
...Dropbox/iPhoto%20Library/Database/albums/
...Dropbox/iPhoto%20Library/Database/apdb/
...Dropbox/iPhoto%20Library/Database/bigblobs.apdb
...Dropbox/iPhoto%20Library/Database/Faces/
...Dropbox/iPhoto%20Library/Database/faces.db
...Dropbox/iPhoto%20Library/Database/folders/
...Dropbox/iPhoto%20Library/Database/History/
...Dropbox/iPhoto%20Library/Database/History.apdb
...Dropbox/iPhoto%20Library/Database/ImageProxies.apdb
...Dropbox/iPhoto%20Library/Database/Keywords.plist
...Dropbox/iPhoto%20Library/Database/Library.apdb
...Dropbox/iPhoto%20Library/Database/places/
...Dropbox/iPhoto%20Library/Database/Properties.apdb
...Dropbox/iPhoto%20Library/Database/Vaults/
...Dropbox/iPhoto%20Library/Database/Versions/
...Dropbox/iPhoto%20Library/Database/Volumes/