Interestingly, the GPS location from your cell-phone 911 is not better than calling security. MIT people are supposed to have 617-253-1212 programmed into their cell phones for emergencies (in case they can't dial "100" on an MIT landline). It is better to call the local security, for all the other reasons given.
A few other details:
* Cell phones have emergency dialing features, including allowing dialing when the phone is locked. There is also the (dubious) feature that once the emergency number (i.e. 911) is dialed (whether the phone is unlocked or locked), the phone then becomes locked so that other calls cannot be dialed or received! Only 911 is allowed in or out. I have found that to be a bad idea and terribly confusing in practice. In any event: Is it possible to have cell phones support more than one emergency number? So you could choose "100" and have it speed dial "617-253-1212" for you? And still recognize "911"?
* At MIT you are actually getting a highly trained "security" person -- you're getting an MIT Police Dispatcher. MIT Campus Police are specially trained State Police officers. Also, MIT has it's own medical center on campus, although I don't know if it's a good trauma center - I bet the ambulance takes you downtown to a "real" emergency room at one of the city hospitals. Are the emergency responders at random companies as well trained? Or are they just minimum wage monkeys who took a CPR course?