I work on a U.S. government crisis/suicide hotline as a rescue coordinator. We receive phone calls, (mostly cell) text and chat from all over the world. Most times the caller/chatter will not disclose their idenity. When the crisis responder feels that a person is a danger to themself or others, I take over to try to identify and locate the person and dispatch the correct emergency response. 

We also get many prank calls. Our states protocol we will not report prank calls to any authority as one day that person may acually need assistance and we do not want to ever discourage a caller form utilizing our service.

When a person calls in, even if they have blocked their number, it is captured by a program we utilize, but only the number is dispalyed; no other info is available. In this case we ask law enforcement to ID/ping the subscriber via the service provider.
When a person is coming in through chat the only thing we have is an IP address. Again, we contact law enforcement and ask them to find a location through the ISP.
There are times when a tech from AT&T or another ISP will say that the IP is not traceable but cant explain why. For instance the last time this occured the IP was a satic coporate IP and tech stated that it didnt seem to be an open proxy but could not find out who/what this IP address was assinged to. 

While I have a basic understanding of the technology I dont understand why the ISP could not ID the subscriber. I am familar that an internet user is able to hide thier IP by using a proxy server and some what understand how an IP can be hidden with a router in home (I think). I also underssatnd that cell providers like T-Mobile are now allowing calls via WiFi, and I assume that these calls can not be traced? Additonally some chatters are using a mobile device (I-Pad, smart phone) to come in over chat...also untraceable?

What I am looking for is a better understanding of how things work with regard to IPs so I can better maximize my effort, as some times lives do hang in the balance. I also pass this on tho the other coordinators and supervisors. This hotline is only 7 years old and I have had to train myself and others to increase the percentage of sucessful "finds" of those in crisis who are handed over to us in order to get help on the way.

Thank you,
John G.

P.S. I am not up on all the acronyms

Addendum: When I receive a "consult" from a responder it is because the chatter is threatening, or in the act of, suicide, or threatening another. It is exigent..."happening now". We are a 24/365 operation. We need to locate/ID the chatter ASAP to dispatch Police/EMS. Would contacting google give us any advantage over what we do now...looking up the IP address for the ISP and asking that ISP for subscriber info to give to police? What I am trying to learn is 2 fold: What more can/should I do when an ISP says it cant be traced and; be able to determine (understand why) what circumstances/ criteria to look for to assess those untraceable IPs so as not to waste vauble time on a lost cause and move to the next rescue. (we recieve about 1000 calls a day and do about 36 rescues. Some can take several hours)