^^ Thanks Curt. I had seen those shots.
Using the tried-and-tested technology, I would assume that all crowd scenes could be gathered and imaged as per the OP link to the the Vancouver Canucks Fan Zone taken before the riots.
Why would police/government agencies therefore not have been taking high resolution crowd surveillance images before and during and after the Boston event? I mean, if they were already running a bomb-threat exercise including rooftop surveillance, Navy Seals and sniffer-dogs...?
It may be that the Boston high resolution images haven't been made publicly available as they are confidential surveillance images for use only by police/government agencies, and could infringe on someone's privacy rights, or something.