I got some great feedback on twitter when I said I was going to give this talk. Two in particular stood out - @realbelahzur wrote this blog and focused on one particular aspect - the theft of service, how far a network operator has to go and the responsibility a user must also take in keeping their own property safe. @paul_clarke pointed me at his blog about his experience of blocking and unblocking a phone.
The slides and notes from the presentation are re-posted here. Please feel free to tweet me and leave comments on your theft experiences and ideas for helping to deal with / manage the problem.