Unfortunately you don't find this out until you wonder why your stuff isn't showing up in a tagged stream and you complain, and then they tell you that:
Your photostream has been marked NIPSA (Not In Publics SiteSo they stealthily scan your photos, or respond to complaints, or some other method they don't reveal, and then they stealthily mark you as "not for public consumption" and don't tell you until you ask why it is that you've been censored. That's really flicked-up. My guess is that they decided that notifying people who are on that list would result in a shitstorm of complaints and customer service contact and expense and stress, so they're just going to do it silently and only deal with the small number of people who notice.
Areas) as you have a number of photographs in your stream that are lifted from the web (copyrighted). If you remove them, we can review your stream again.
You know, I bet a lot of Flickr's customers don't pay attention to that rule, and I bet a lot of them are "NIPSA" and don't know it. And I bet that makes their whole system less effective.
Once again I agree completely that their terms of service make sense and that people should follow them. But can't they come up with something better than the Homeland Security No-Fly List model? Way to inspire paranoia, guys.