Michael, my interpretation of what David was saying of crowd based photo collections not being so useful for 3D reconstruction was that this was the case because people only shoot landmarks from a very limited range of positions, never bothering to walk all the way around a building and shoot photos of the sides or back.
In that sense, it isn't so much the case that the photos in existing online collections don't have the right features, but rather that they don't come from a deep enough range of positions. I think from the front of the building or monument, such collections probably have all the features that one could wish for, in order to construct the front facade (although not perhaps as thorough as systematic coverage designed to build fine grain pointclouds of every light fixture or relief on the front of said building).
The question now is only how to fit all the photos into one synth.
Apologies if that is what you intended to communicate to begin with.