Social Sensing. Dalla rete agli utenti e ritorno

The current Social Media platforms enable millions of people each day to share information and document events in real time. Would it be possible to utilize Social platform users as sensors to be employed when events in the real world occur? In the case of a natural disaster, but also of a terrorist attack, would it be possible to ask users of the network present on the spot to share in the immediacy information relative to that event?