I can see both sides on this. I do think that such data when used responsibly can really help in solving serious crimes. But, as you say, there is a serious dan

I can see both sides on this. I do think that such data when used responsibly can really help in solving serious crimes. But, as you say, there is a serious danger of law enforcement abusing the system and gathering far more data than they need. It's not like they haven't been guilty of such abuses in the past. Look at the situation with gathering fingerprints or DNA and then not scrubbing the data of innocents once an investigation has finished. I am wondering if the solution is to have an independent service. One that would sit as a middleman between police and technology companies such as Google. Their mandate would be to provide the minimum amount of data required for an investigation (the example used in the article is a good one, where anonymous data for a particular location at a particular time-frame is requested and used to narrow down the search and then get more information on a subset of that data). They could be required to keep logs of what is being requested and what is being provided and could be audited at intervals by, say, the EFF. Obviously this is only a rough sketch of the idea, it would need fleshing out more completely.