It is rare for secondary uses data to get such an airing on Mumsnet I must say.
Argy is right in that primary clinical records aren't shared very much (more than not at all, in some places, depends on what systems you are using). Episode information is submitted for secondary uses, from billing and service planning to research, workforce planning and casemix.
HES/SUS is identifiable. However, I have already linked to the Data Access Request Service which gives details of the scrutiny required for anyone to request an identifiable extract. Most users of the data do not require it to be identifiable.
I believe that DARS was set up in response to a story I have already linked to above, in which the Information Centre was found to have breached the rules on sharing identifiable data.
The problem of reidentification of small record sets is real.
All of which highlights what has been said in a report I really cannot be arsed linking to yet again, which is the public need to have the opportunity to be informed. Most members of the public, as evidenced on this thread, are happy for their data to be shared both in support of their own care and in the secondary functions of the NHS. Some are not. Both groups need to have reasonable allowances made for their wishes to be respected.
I genuinely hope most posters on this thread have learnt something and I think it's been very useful in this regard. I would say that anecdote is not evidence and privacy concerns may appear more real when backed up by fact.