What are the advantages of having the public be an active participant in the collection of data?

What is the GeoHub? How is it useful to the city of Los Angeles? What are the advantages of having the public be an active participant in the collection of data? What are the disadvantages? What role does data visualization play in having community members better understand and manage their local resources? How might that influence local decisions and policy making? What are some common types of challenges in storytelling on social media?http://geohub.lacity.org/https://drive.google.com/file/d/0B4Rsq2eS6qMGSUk2WEU1SlhiMlk/view