At my house, I'm careful at 15 yards, but it rarely an issue. If they have no calves and they have escape options, and I'm doing something else (not approaching or stalking them), then they're cool. There certainly are times when we surprise each other at 4 to 10 feet in the dark, but that usually feels too close to me and apparently to them.
The kids fondly recall "moose petting season" – that second week of May when the calves have been chased off by mom and wander around kind of lost, looking for a friend. One came up to us in the hot tub and my 10 year old petted him on the nose.
Bob is right about them filling the frame. A few times each month, I'll look up from my computer, initially puzzled why the entire viewscape out the window is brown fur. It means they're nibbling the petunias again. Moose look much better from a distance. Up close, they have these warty growths on their hindquarters, their fur is often mottled and coming off in chunks, and there's often a big cloud of mosquitos following them around.