It seemed that you were condoning all invasions of privacy because you found a few instances where it might be appropriate. I think that is the objectionable part in contention.
I apologise if I gave that impression. I am not intending to argue that position at all. In fact, my personal stance seems very similar to yours (starting where you wrote, "The problem here is not invasion of privacy per se, but unrestricted invasion of privacy.").
I had hoped that this would be clear from my repeated references throughout this discussion to questions of degree and to the need to control the reuse of data by other parties or for other purposes than those for which it might originally have been collected legitimately. I'm very sorry if that wasn't the case.
The only point I'm trying to make regarding compulsory collection of data by governments is that I think in practice some level of invasion of privacy is inevitable, and indeed desirable, for our society to function effectively. I agree that in theory we could move to a radically different form of government and government funding, but I think is not going to happen any time soon, so for now we need a fair (in the objective sense of being published and equally applicable to all citizens) set of rules for running that government and for providing resources to it. I think this inevitably requires some basic information about those citizens, for example to ensure that elections can be (and are seen to be) properly representative, even if not everyone chooses to exercise their right to vote.
Personally, I have no problem with governments collecting information for that kind of purpose. I think it's in everyone's interests, and it's possible to have information about who has a right to vote without using it for any other purpose. Things get more controversial when you start repurposing that information. For example, in the UK, the electoral roll is also used for various identity checking purposes, for identifying candidates for jury duty in courts, and for fundraising by local authorities who sell the contents of the roll to marketing organisations. The degree to which these reuses of that information are acceptable is a far more interesting debate to me than whether we should have a compulsory electoral registration process every year that requires everyone to confirm who is eligible to vote in their household.