The last type of privacy to speak about is the privacy of the association.
Privacy of association (including group privacy), is concerned with people's right to associate with whomever they wish, without being monitored. This has long been recognised as desirable (necessary) for a democratic society as it fosters freedom of speech, including political speech, freedom of worship and other forms of association. Society benefits from this aspect of privacy in that a wide variety of interest groups will be fostered, which may help to ensure that marginalised voices, some of whom will press for more political or economic change, are heard.
With the development of internet, the idea of association became really visible. Yesterday you knew, that there was a guy somewhere on the other side of planet which likes Alladin 2 on SEGA and knows everything about the game. And when you enter the kingdom of world wide web, you enter "Alladin 2" in some ancient search engine (of course, after entering "ass" or something similar just to double check that internet is fun) and voila - you find a whole club of Alladin 2 lovers.
Association works strangely. Every respectful social network gives you an opportunity not only to create your own network of friends, but even to join the existing ones.
Be aware, if you join that groups - they know more and more about you again. Again you associate yourself with a group of coin collectors and a group of art-noveau lovers. Careful with that, not-a-democratic society will consider you to be a part of bourgeoisie, and nobody likes it, believe me.
Probably, the good news is - I've never felt, that associating myself with any group nowadays really works against me. Probably there's no chance now to create a group, which would be small enough to be called minority?