My understanding about O2 was that it was a misconfigured proxy - they usually send your mobile number as a header to some internal sites (for example, you can

My understanding about O2 was that it was a misconfigured proxy - they usually send your mobile number as a header to some internal sites (for example, you can check your pay-and-go account balance without logging in, IIRC), but managed to misconfigure it so it sent your number everywhere. They removed it ASAP, not putting up any sort of fight, so I suspect that's truly the case. An article on the subject, from the same source: http://www.theregister.co.uk/2012/01/25/o2_number_sharing/ http://www.theregister.co.uk/2012/01/25/o2_number_sharing/