After reading the above (very good) responses, I figured maybe I ought to clarify, or at least reconsider, my above post. When I read it initially, I took the question to mean, “Do you think that you should WARN other hikers whenever you see a bear, or come across a bear while hiking?”. In that context, I still would say it DEPENDS, but I would certainly weigh a few more factors before dispensing "warnings". Giving a WARNING, and giving a “WOW, you’ll never guess what I just saw.” Are two separate things IMO. One implies caution, the other does not.
Circumstances – Like I said, it would depend what the bear was doing when I saw it. If the behavior struck me as odd or predatory, I would get the hell out of there and tell everyone I saw about it. But if it was just acting like a rumbling, bumbling ordinary bear, I probably would not.
Example -once practically walked into a bear as just above Indian Falls as I was walking up the trail to Marcy and it was coming down. We saw each other (from about 15-20’ and it just scampered off after about 2-3 seconds. I told my hiking group (including my kids) a few minutes later so as not to alarm them, but as I never felt threatened or scared, so I didn’t feel any need to “alarm” every hiker I saw over the next 8 hours of my encounter.
Time & distance – Using my situation above, had I run into anyone (other hikers) in the hour (or couple miles) after my sighting, I might be much more likely to mention it if we started chatting then I would if it were 4 hours outand I’m miles from where it happened.
Dogs – I guess I never really considered this one, mostly cause I rarely hike with dogs. But given the above responses, I guess it would be prudent to let hikers with dogs know as dogs may increase the chance of interaction. I’d give them a LARGER “warning area” than non-dog hikers, but again, after a point the sighting does become irrelevant as it pertains to "caution".
I think Mark’s post displays an attitude that is similar to mine.
I’m REAL cautious about the “alert any and all” school of thought. Maybe it’s wrong of me, but I would hate to “ruin” someone else’s hike by needlessly "WARNING" them that a bear has passed. There are lots of hikers that have an overly active fear of bears. My daughter sometime displays this fear and I remember recently while hiking, we came across some scat. Now, this poop was so fresh, it was still smoking. I’m willing to bet the bear that deposited it was still within shouting distance. I never said a word and we never saw, nor heard the animal in question... end of story. I could’ve gone the other way and given the ole’ “Wow, this crap is so fresh honey, that big bruin must still be nearby, SO stick close to daddy”.
Had I done that, that bear would have been stalking her around EVERY tree for the rest of that hike (and more), at least in her own mind. She would have been miserable, needlessly. My way, she went on blissfully unaware and had a wonderful hike.
Like everything else, use good judgement and common sense should prevail in this and you'll be fine.