I think the concern about bears is over-rated, and over discussed on the internet. I have done a good bit of hiking in the Appalachians and in the Rockies and Yellowstone. Bear encounters are few and far between.
I am MUCH more worried about running into weird people than man-eating animals.
Since I think bear encounters are rare, and human encounters more common and probably more dangerous anyway, I am not so much a fan of the 44 magnum as other people. Yes, I think the 44 mag would be better if you have an encounter with a grizzly, but that is unlikely even in the west, and impossible in the east. I think you should have a gun that is better suited to the type of hostile encounter that is most likely, and that is with other people. I have done most of my hiking with a 9mm or 10mm auto (Glocks). In the Appalachians, I am very comfortable with 9mm. Out west, I would rather have the 10mm. I think a G20 is a wonderful compromise between power, weight, and ammo capacity.
If they ever find the bear-eaten remains of a guy armed with an empty, slide-locked Glock in his hand, its probably me, and you better believe the last thing I was thinking was how much I would rather have had a 44 mag.
To those that advocate the .500 S&W, I would ask, have you ever actually hiked with one for a long distance? It would seem to me that it would be difficult to keep concealed from other hikers, and in many areas you pretty much have to keep it concealed to keep from getting reported. Also, the sheer weight of the weapon would be prohibitive to most back packers.