> If the data is truly anonymized (and that's a big if), would you still have an issue?
Yes!
It's simply not anyone's matter to decide but the affected person what their data is used for, if only because that destroys trust. It is critical to the relationship between doctors and patients that the patient doesn't feel any need to hide information because they think that it might be shared and used against them, even when that fear might not actually be justified by the actual facts of the situation.
Also, that big if of anonymization is an important reason why the decision should be for the individual to make, if it is allowed at all: If you distrust the anonymization, then you should be able to refuse, without any requirement on your part to prove that it is unreliable.
Yes!
It's simply not anyone's matter to decide but the affected person what their data is used for, if only because that destroys trust. It is critical to the relationship between doctors and patients that the patient doesn't feel any need to hide information because they think that it might be shared and used against them, even when that fear might not actually be justified by the actual facts of the situation.
Also, that big if of anonymization is an important reason why the decision should be for the individual to make, if it is allowed at all: If you distrust the anonymization, then you should be able to refuse, without any requirement on your part to prove that it is unreliable.