You're right that there is a difference between face to face conversations and digital tracking. That's why I'm weaseling out with my "first party" qualifications. As long as the tracking is between you and the site you're on, it's sort-of similar to personal conversations. Not the same, but not super different. As soon as third parties and groups of people and governments are involved, it's wildly different.
The camera issue is interesting. This will be a growing concern from now on. According to US law, there is no expectation of privacy from being photographed while you're in a public place. You are not currently entitled to privacy in a library, or while walking downtown, or while driving in a car on public roads. But that law wasn't drafted with the idea of digital mass surveillance in mind, nobody had the capability to capture and correlate all your movement when it was written.
This is why I explicitly talked about browsing of books at the library, not checking them out.
But now that you mention it, tracking who checks out which books also has disturbing privacy implications, and I am against that. There's nothing stopping an anonymous library checkout system from being designed and implemented, if we only had the will.
Camera use in libraries is a relatively new phenomenon, and I'd have similar privacy concerns about it if, like website tracking, its explicit aim was to track who was looking at which books, but as far as I know it's not being used for that purpose. But it's not very far from being capable of doing that, especially with high resolution cameras and facial recognition systems. So that's definitely something to keep an eye on.
"Talking to a person face to face has exactly the same issues. If I buy a car, for example, the sales guy will definitely watch my gaze and listen to what I say with an ear toward exploiting anything I share with him to increase his odds of selling me a car. We wouldn’t call what the sales guy does a privacy issue"
I would in fact call that a privacy issue. We're just so used to it we don't normally notice it. There's also an enormous difference between one person noticing your interest in one thing and the systemic, omnipresent surveillance apparatus we've made the internet in to, which is tracking all your interests, and voiced opinions and ideas.
Look at the repression, imprisonment, murder of political or ideological opponents throughout history, and you'll see their surveillance, tallying, and location has always been a part of that. Today's surveillance apparatus is thousands or millions of times more effective than it's ever been in the past, and every bit of data collected about you feeds in to those profiles which could be used against you. We should oppose it, instead of meekly submitting to it, much less enabling it.