User's time and bandwidth are valuable commodities. To safeguard these resources, people engage in social activities which exclude people likely to waste their time. There are entire industries that peddle influence through social engineering to penetrate this approach. Surely I don't need to spell these out ... ;D. But you don't see much of the activity you are interested in here at HN, and when you do the evicence suggests it is the exceptions that prove the rule. And also when those exceptions are not in place it is the typical case demonstrating the case quite nicely.
The issue about "better targeting" is that the delterious elements of advertising do not go away. This is the reason why sometimes we decline to take a phone call in the middle of the meeting. Its not always the targeting, the content, or the message that it counter-productive. Sometimes it is the time and the context.
So it is not just that privacy is protected, or not. Nor is it sufficient that "better targeting" should be an excuse to increase attack surface for placing adds; or that "more secure" should increase the attack surface for data-intensive surveilance and information gathering.
Part of the art of marketing is reaching people in a constructive way. Advertising is not always the way to do that. No matter how "well targeted" it is. That is why we have PR and lobbying, informal networking, social circles, and country clubs, alumni networks...etc. And why we don't accept advertisments in front of phone calls like we do at the movies. Etc.