I work in a small office with a lot of downtime, and we have a new employee with wandering eyeballs. He always seems to have a rather obvious eye on what everyone else is doing, including his coworkers.
Our job involves being attentive to what's going on because clients may or may not need help, but at least I can be subtle about watching people because I understand that it can put people on edge or I could be looking at something private if I walk up behind them and help myself. I also don't track what my coworkers are doing because they're not my responsibility, and treating their activities like my responsibility is rude.
New Guy is at least 10 years older than the rest of us and tends to wander around when he's not busy like a teacher checking progress in the classroom (the rest of us tidy up, skim a book from a shelf, or chat until we're needed again), so I almost get the impression that he thinks he's in an unofficial position of authority here.
How do you handle nosy coworkers who aren't technically out of bounds?