Re: Not wanting to defend plod, but
There's no "alleged tracability". If you connect via FON, you arrive on the Internet via a completely public IP address using logon credentials. The traffic is just as traceable as that for any traffic coming from a device connected to your home network. Indeed, more so as there are not credentials passed from devices on your home network to the ISP (unless there's a back-door in the router which logs MAC addresses and sends them to the ISP).
Of course, somebody could always steal your details, but that is true of any public network where you logon with a userid and password. Indeed, it's true of somebody who gains access to your home network logon details (how many people freely give their WiFi passwords to friends and family to put in their phones and other devices; how secure are those?). The only systems which are really proof against stolen details are where one time password devices are required.
This is plod knowing a little and thinking he's somehow qualified to lecture the world. If he wants a security problem to worry about, then it's about accessing public networks at all. It would be pretty easy to mimic a BT FON connection.