CDRs - Call Detail Records, the database entities that permit telcos to bill their users - are getting a bad press at the moment with the latest revelations about US networks' willingness to let the NSA dig through their databases without getting warrants or accepting any other quaint legal restrictions.

But at Telco 2.0 yesterday, we heard how CDRs might actually empower the users in a Telco 2.0 future. Keith Wallington of mobile SIP insurgents Truphone suggested that "in the future, this will be bigger than mobile number portability". Wallington proposed the ability to have calls routed intelligently depending on your preferences and the patterns of use revealed by network data. And this brings us right to his point.

If all your contextual services depend on the contrail of signalling data you leave behind in the operator network, the ability to take that information with you when you churn is going to be crucial. Perhaps we need a right to claim our data; however, the really important point is as always the practical implementation of such a thing, just as it was with number portability.

So, of course, are the legal and privacy problems; the incentives for the operator to implement a platform for interesting contextual services are all about the clever things the operator could do with the data, but the strongest protections for user privacy essentially rule this out. If the user data, for example, was encrypted with a key the user controlled, the user could grant access to it for each service they wanted. But the operators will insist on being able to analyse the data themselves; or they probably won't do it.