[shoemakersteve]

I think I see where you're coming from, in that you're allowed to have knowledge of other people, and most of the time it's perfectly innocuous. But I don't think that's a very fair comparison. There's a pretty big difference between just happening upon some information (that you would likely immediately forget because it's not important), and actively seeking out and extracting information, often combining it with more information from different sources, saving it to a "profile" associated with you, and often sharing it with third parties, all without your knowledge or consent.

You seem to be implying that there's no difference between having a single piece of harmless information about someone, and having lots of personal and/or intimate knowledge of them, especially if they aren't the ones having given it to you, and even more so if you're strangers.