Well look at it like this: if you actively don't want to pay your taxes (for whatever political reason), a small message saying "your neighbours paid their taxe

Well look at it like this: if you actively don't want to pay your taxes (for whatever political reason), a small message saying "your neighbours paid their taxes" won't sway you, but if you have had it in the back of your mind that you need to pay your taxes, you just don't want to go through all the hassle of doing it right now, maybe that's the message you need to motivate you. It's not really any sort of behaviour modification, they aren't even lying. It does go against the simple idea of total individuality and complete freedom, so that's probably why it makes you feel uncomfortable. Also anything the government does "in my interest" makes me deeply suspicious on principle. In this case though, I can't see anything really wrong with it.