I think this is a huge issue - and the government are relying on people reading the leaflet, wrongly assuming that this will help them in some way should they turn up unconscious at A&E miles from home, that it is anonymous and could be used to further medical research, and so on.
The fact that it is bloody difficult to opt out, that they are not even bothering to send a letter to each household but sending out junk mail that will be easily overlooked or missed, that they are stripping out just names from the data when they could have chosen to strip out many more details to make it much more anonymous, the fact that the 'researchers' that the data can be released to include companies who will be able to profit from it (and often at your expense) and so on, is all a huge red flag that this is not a good thing. If it was such a good thing for individuals that they would want to sign up for, then they would have let people opt in. But when there is something tricky like this, the way that they make it happen is to choose the default option as the one that they want and put as many obstacles as they can in the way of letting people opt out.
How are people going to like it when Tesco buys the database to cross with their clubcard database and it will then be pretty easy to figure out who is who as they will have several overlapping data points for each person - when you start getting offers for weight watchers baked beans and oats because you are flagged as being overweight - or tena lady pads as you'd enquired about being a bit leaky or pregnancy stuff because they saw that you were pregnant (even before you have started to tell your own family!) and all other sorts of promotions that would be incredibly intrusive and you wouldn't want others to know about, let alone handing over vouchers to the person on the checkout.
I know the medconfidential site, as already mentioned, and a few others are doing great things to try to raise awareness of this. I wonder if this is something that Mumsnet could use it's clout to raise awareness of two - even just by putting a fixed link at the top of the active list for a couple of days, along with links to the forms for opting out. What do people on here think?
If the government were truly interested in doing epidemiological studies with the data then they could have really made it anonymous and they could have restricted access to proper epidemiological researchers. Letting anybody who waves cash in front of them and who has the resources to have their own database or access to the electoral role and can thus just stick names back on to the data means that this has been set up purely and simply to flog and get money from.