All I really can see in the future with such idea is people suing the police department for not acting or not acting fast enough. Not only that but trying to track your signal incase you are not able to continue the text in order to give more information so a police officer can get there ASAP. In the USA it's all about suing. This country it's great for many things but not everything.
To give you some perspective to this poll, read this CNET article: Text-to-911: What you need to know (FAQ)
Do you think there are any disadvantages to Text-to-911 service?
-- Yes. (What is it?)
-- No. (None at all?)
-- Not sure. (What are you hung up on? (No pun intended.)
Vote here: http://forums.cnet.com/2706-21566_102-2415.html

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