Law enforcement agencies have mined posts on Facebook, Twitter, Instagram, YouTube and other sites during parades, protests and other large events. One company marketing the technology suggested police track hashtags such as #BlackLivesMatter and #ImUnarmed. Police used its software during protests over the death of Freddie Gray, Denver's annual marijuana rally and Martin Luther King Day march and parade. "These programs are a deterrent to free speech," said Baltimore activist Kwame Rose.
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